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	$233.32	7.519%	$250.8633	$250.86	$250.85	$250.90
Purchase #2	$195.66	7.588%	$210.5067	$210.51	$210.50	$210.50
Purchase #3	$142.91	11.657%	$159.569	$159.57	$159.55	$159.60
Purchase #4	$86.99	9.676%	$95.4072	$95.41	$95.40	$95.40
Purchase #5	$60.94	3.736%	$63.2167	$63.22	$63.20	$63.20
Purchase #6	$16.85	7.848%	$18.1724	$18.17	$18.15	$18.20
Purchase #7	$212.48	4.396%	$221.8206	$221.82	$221.80	$221.80
7 purchase totals =	$949.15		$1,019.5559	$1,019.56	$1,019.45	$1,019.60