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	$248.72	8.127%	$268.9335	$268.93	$268.95	$268.90
Purchase #2	$143.79	6.191%	$152.692	$152.69	$152.70	$152.70
Purchase #3	$223.40	4.743%	$233.9959	$234.00	$234.00	$234.00
Purchase #4	$93.89	10.418%	$103.6715	$103.67	$103.65	$103.70
Purchase #5	$56.48	8.628%	$61.3531	$61.35	$61.35	$61.40
Purchase #6	$117.98	8.722%	$128.2702	$128.27	$128.25	$128.30
Purchase #7	$95.56	7.560%	$102.7843	$102.78	$102.80	$102.80
7 purchase totals =	$979.82		$1,051.7005	$1,051.69	$1,051.70	$1,051.80