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	$148.96	6.243%	$158.2596	$158.26	$158.25	$158.30
Purchase #2	$231.44	3.770%	$240.1653	$240.17	$240.15	$240.20
Purchase #3	$211.54	7.220%	$226.8132	$226.81	$226.80	$226.80
Purchase #4	$38.94	11.413%	$43.3842	$43.38	$43.40	$43.40
Purchase #5	$59.72	5.105%	$62.7687	$62.77	$62.75	$62.80
Purchase #6	$223.54	10.599%	$247.233	$247.23	$247.25	$247.20
Purchase #7	$133.83	6.304%	$142.2666	$142.27	$142.25	$142.30
7 purchase totals =	$1,047.97		$1,120.8906	$1,120.89	$1,120.85	$1,121.00