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	$60.86	7.414%	$65.3722	$65.37	$65.35	$65.40
Purchase #2	$188.92	3.874%	$196.2388	$196.24	$196.25	$196.20
Purchase #3	$142.83	7.250%	$153.1852	$153.19	$153.20	$153.20
Purchase #4	$120.77	5.790%	$127.7626	$127.76	$127.75	$127.80
Purchase #5	$117.43	13.730%	$133.5531	$133.55	$133.55	$133.60
Purchase #6	$236.41	3.449%	$244.5638	$244.56	$244.55	$244.60
Purchase #7	$109.86	11.271%	$122.2423	$122.24	$122.25	$122.20
7 purchase totals =	$977.08		$1,042.9180	$1,042.91	$1,042.90	$1,043.00