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	$148.90	4.756%	$155.9817	$155.98	$156.00	$156.00
Purchase #2	$130.86	8.323%	$141.7515	$141.75	$141.75	$141.80
Purchase #3	$159.43	12.454%	$179.2854	$179.29	$179.30	$179.30
Purchase #4	$229.36	6.317%	$243.8487	$243.85	$243.85	$243.80
Purchase #5	$95.79	5.228%	$100.7979	$100.80	$100.80	$100.80
Purchase #6	$51.70	6.323%	$54.969	$54.97	$54.95	$55.00
Purchase #7	$37.94	11.811%	$42.4211	$42.42	$42.40	$42.40
7 purchase totals =	$853.98		$919.0553	$919.06	$919.05	$919.10