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	$221.32	3.360%	$228.7564	$228.76	$228.75	$228.80
Purchase #2	$105.32	8.568%	$114.3438	$114.34	$114.35	$114.30
Purchase #3	$174.50	12.825%	$196.8796	$196.88	$196.90	$196.90
Purchase #4	$226.54	3.344%	$234.1155	$234.12	$234.10	$234.10
Purchase #5	$161.96	11.377%	$180.3862	$180.39	$180.40	$180.40
Purchase #6	$52.60	10.764%	$58.2619	$58.26	$58.25	$58.30
Purchase #7	$34.57	13.188%	$39.1291	$39.13	$39.15	$39.10
7 purchase totals =	$976.81		$1,051.8725	$1,051.88	$1,051.90	$1,051.90