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	$149.43	11.599%	$166.7624	$166.76	$166.75	$166.80
Purchase #2	$70.53	10.401%	$77.8658	$77.87	$77.85	$77.90
Purchase #3	$198.89	12.787%	$224.3221	$224.32	$224.30	$224.30
Purchase #4	$14.97	8.393%	$16.2264	$16.23	$16.25	$16.20
Purchase #5	$249.34	11.822%	$278.817	$278.82	$278.80	$278.80
Purchase #6	$221.33	13.354%	$250.8864	$250.89	$250.90	$250.90
Purchase #7	$166.39	11.685%	$185.8327	$185.83	$185.85	$185.80
7 purchase totals =	$1,070.88		$1,200.7128	$1,200.72	$1,200.70	$1,200.70