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	$157.29	4.675%	$164.6433	$164.64	$164.65	$164.60
Purchase #2	$196.83	13.390%	$223.1855	$223.19	$223.20	$223.20
Purchase #3	$111.89	7.853%	$120.6767	$120.68	$120.70	$120.70
Purchase #4	$173.82	3.349%	$179.6412	$179.64	$179.65	$179.60
Purchase #5	$76.37	4.111%	$79.5096	$79.51	$79.50	$79.50
Purchase #6	$56.75	13.343%	$64.3222	$64.32	$64.30	$64.30
Purchase #7	$174.97	8.205%	$189.3263	$189.33	$189.35	$189.30
7 purchase totals =	$947.92		$1,021.3048	$1,021.31	$1,021.35	$1,021.20