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	$120.67	9.202%	$131.7741	$131.77	$131.75	$131.80
Purchase #2	$83.28	7.439%	$89.4752	$89.48	$89.50	$89.50
Purchase #3	$214.46	3.379%	$221.7066	$221.71	$221.70	$221.70
Purchase #4	$163.84	6.243%	$174.0685	$174.07	$174.05	$174.10
Purchase #5	$80.85	12.513%	$90.9668	$90.97	$90.95	$91.00
Purchase #6	$134.47	9.122%	$146.7364	$146.74	$146.75	$146.70
Purchase #7	$221.78	5.232%	$233.3835	$233.38	$233.40	$233.40
7 purchase totals =	$1,019.35		$1,088.1111	$1,088.12	$1,088.10	$1,088.20