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	$215.34	4.240%	$224.4704	$224.47	$224.45	$224.50
Purchase #2	$148.29	5.126%	$155.8913	$155.89	$155.90	$155.90
Purchase #3	$230.27	13.663%	$261.7318	$261.73	$261.75	$261.70
Purchase #4	$77.38	4.258%	$80.6748	$80.67	$80.65	$80.70
Purchase #5	$184.73	3.434%	$191.0736	$191.07	$191.05	$191.10
Purchase #6	$105.80	6.215%	$112.3755	$112.38	$112.40	$112.40
Purchase #7	$89.56	9.740%	$98.2831	$98.28	$98.30	$98.30
7 purchase totals =	$1,051.37		$1,124.5005	$1,124.49	$1,124.50	$1,124.60