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	$158.52	13.223%	$179.4811	$179.48	$179.50	$179.50
Purchase #2	$86.52	5.152%	$90.9775	$90.98	$91.00	$91.00
Purchase #3	$119.46	12.352%	$134.2157	$134.22	$134.20	$134.20
Purchase #4	$115.50	4.312%	$120.4804	$120.48	$120.50	$120.50
Purchase #5	$66.61	9.548%	$72.9699	$72.97	$72.95	$73.00
Purchase #6	$235.34	5.744%	$248.8579	$248.86	$248.85	$248.90
Purchase #7	$190.32	3.788%	$197.5293	$197.53	$197.55	$197.50
7 purchase totals =	$972.27		$1,044.5118	$1,044.52	$1,044.55	$1,044.60