Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$105.49	3.639%	$109.3288	$109.33	$109.35	$109.30
Purchase #2	$158.50	13.107%	$179.2746	$179.27	$179.25	$179.30
Purchase #3	$180.73	5.671%	$190.9792	$190.98	$191.00	$191.00
Purchase #4	$112.83	10.706%	$124.9096	$124.91	$124.90	$124.90
Purchase #5	$206.73	13.614%	$234.8742	$234.87	$234.85	$234.90
Purchase #6	$196.59	7.356%	$211.0512	$211.05	$211.05	$211.10
Purchase #7	$214.60	13.740%	$244.086	$244.09	$244.10	$244.10
7 purchase totals =	$1,175.47		$1,294.5036	$1,294.50	$1,294.50	$1,294.60