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	$122.56	12.305%	$137.641	$137.64	$137.65	$137.60
Purchase #2	$41.98	7.768%	$45.241	$45.24	$45.25	$45.20
Purchase #3	$118.39	4.820%	$124.0964	$124.10	$124.10	$124.10
Purchase #4	$118.93	8.111%	$128.5764	$128.58	$128.60	$128.60
Purchase #5	$91.28	6.643%	$97.3437	$97.34	$97.35	$97.30
Purchase #6	$104.78	8.313%	$113.4904	$113.49	$113.50	$113.50
Purchase #7	$99.96	12.362%	$112.3171	$112.32	$112.30	$112.30
7 purchase totals =	$697.88		$758.7060	$758.71	$758.75	$758.60