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	$215.84	3.155%	$222.6498	$222.65	$222.65	$222.60
Purchase #2	$137.28	10.113%	$151.1631	$151.16	$151.15	$151.20
Purchase #3	$128.53	11.116%	$142.8174	$142.82	$142.80	$142.80
Purchase #4	$79.78	4.792%	$83.6031	$83.60	$83.60	$83.60
Purchase #5	$152.35	11.822%	$170.3608	$170.36	$170.35	$170.40
Purchase #6	$239.69	12.638%	$269.982	$269.98	$270.00	$270.00
Purchase #7	$208.85	9.251%	$228.1707	$228.17	$228.15	$228.20
7 purchase totals =	$1,162.32		$1,268.7469	$1,268.74	$1,268.70	$1,268.80