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	$211.70	5.742%	$223.8558	$223.86	$223.85	$223.90
Purchase #2	$53.70	13.256%	$60.8185	$60.82	$60.80	$60.80
Purchase #3	$102.58	9.807%	$112.64	$112.64	$112.65	$112.60
Purchase #4	$157.32	12.214%	$176.5351	$176.54	$176.55	$176.50
Purchase #5	$178.49	5.616%	$188.514	$188.51	$188.50	$188.50
Purchase #6	$18.89	6.300%	$20.0801	$20.08	$20.10	$20.10
Purchase #7	$80.67	13.666%	$91.6944	$91.69	$91.70	$91.70
7 purchase totals =	$803.35		$874.1379	$874.14	$874.15	$874.10