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	$133.98	4.224%	$139.6393	$139.64	$139.65	$139.60
Purchase #2	$64.59	4.162%	$67.2782	$67.28	$67.30	$67.30
Purchase #3	$34.76	7.614%	$37.4066	$37.41	$37.40	$37.40
Purchase #4	$127.33	6.359%	$135.4269	$135.43	$135.45	$135.40
Purchase #5	$95.31	6.569%	$101.5709	$101.57	$101.55	$101.60
Purchase #6	$94.99	5.803%	$100.5023	$100.50	$100.50	$100.50
Purchase #7	$85.26	12.204%	$95.6651	$95.67	$95.65	$95.70
7 purchase totals =	$636.22		$677.4893	$677.50	$677.50	$677.50