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	$210.73	7.450%	$226.4294	$226.43	$226.45	$226.40
Purchase #2	$95.93	3.716%	$99.4948	$99.49	$99.50	$99.50
Purchase #3	$230.28	6.107%	$244.3432	$244.34	$244.35	$244.30
Purchase #4	$118.88	10.828%	$131.7523	$131.75	$131.75	$131.80
Purchase #5	$240.61	6.717%	$256.7718	$256.77	$256.75	$256.80
Purchase #6	$132.96	7.601%	$143.0663	$143.07	$143.05	$143.10
Purchase #7	$178.41	11.162%	$198.3241	$198.32	$198.30	$198.30
7 purchase totals =	$1,207.80		$1,300.1819	$1,300.17	$1,300.15	$1,300.20