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	$96.87	12.767%	$109.2374	$109.24	$109.25	$109.20
Purchase #2	$189.88	3.373%	$196.2847	$196.28	$196.30	$196.30
Purchase #3	$180.91	8.613%	$196.4918	$196.49	$196.50	$196.50
Purchase #4	$125.27	4.679%	$131.1314	$131.13	$131.15	$131.10
Purchase #5	$153.28	4.454%	$160.1071	$160.11	$160.10	$160.10
Purchase #6	$169.31	13.211%	$191.6775	$191.68	$191.70	$191.70
Purchase #7	$240.32	5.594%	$253.7635	$253.76	$253.75	$253.80
7 purchase totals =	$1,155.84		$1,238.6934	$1,238.69	$1,238.75	$1,238.70