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	$197.38	12.365%	$221.786	$221.79	$221.80	$221.80
Purchase #2	$155.28	4.501%	$162.2692	$162.27	$162.25	$162.30
Purchase #3	$158.51	6.260%	$168.4327	$168.43	$168.45	$168.40
Purchase #4	$187.57	13.419%	$212.74	$212.74	$212.75	$212.70
Purchase #5	$148.72	13.410%	$168.6634	$168.66	$168.65	$168.70
Purchase #6	$88.93	4.314%	$92.7664	$92.77	$92.75	$92.80
Purchase #7	$100.61	13.822%	$114.5163	$114.52	$114.50	$114.50
7 purchase totals =	$1,037.00		$1,141.1740	$1,141.18	$1,141.15	$1,141.20