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	$192.76	11.223%	$214.3935	$214.39	$214.40	$214.40
Purchase #2	$159.94	3.717%	$165.885	$165.89	$165.90	$165.90
Purchase #3	$153.60	4.276%	$160.1679	$160.17	$160.15	$160.20
Purchase #4	$158.60	10.286%	$174.9136	$174.91	$174.90	$174.90
Purchase #5	$152.46	10.277%	$168.1283	$168.13	$168.15	$168.10
Purchase #6	$184.56	6.222%	$196.0433	$196.04	$196.05	$196.00
Purchase #7	$114.30	5.418%	$120.4928	$120.49	$120.50	$120.50
7 purchase totals =	$1,116.22		$1,200.0244	$1,200.02	$1,200.05	$1,200.00