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	$72.52	6.335%	$77.1141	$77.11	$77.10	$77.10
Purchase #2	$125.93	13.449%	$142.8663	$142.87	$142.85	$142.90
Purchase #3	$120.40	9.408%	$131.7272	$131.73	$131.75	$131.70
Purchase #4	$147.98	11.608%	$165.1575	$165.16	$165.15	$165.20
Purchase #5	$132.32	12.309%	$148.6073	$148.61	$148.60	$148.60
Purchase #6	$148.97	9.211%	$162.6916	$162.69	$162.70	$162.70
Purchase #7	$170.70	8.470%	$185.1583	$185.16	$185.15	$185.20
7 purchase totals =	$918.82		$1,013.3223	$1,013.33	$1,013.30	$1,013.40