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	$184.32	10.680%	$204.0054	$204.01	$204.00	$204.00
Purchase #2	$99.91	3.417%	$103.3239	$103.32	$103.30	$103.30
Purchase #3	$49.82	13.499%	$56.5452	$56.55	$56.55	$56.50
Purchase #4	$118.58	7.698%	$127.7083	$127.71	$127.70	$127.70
Purchase #5	$7.82	4.309%	$8.157	$8.16	$8.15	$8.20
Purchase #6	$90.56	9.809%	$99.443	$99.44	$99.45	$99.40
Purchase #7	$191.45	8.113%	$206.9823	$206.98	$207.00	$207.00
7 purchase totals =	$742.46		$806.1651	$806.17	$806.15	$806.10