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	$131.27	13.607%	$149.1319	$149.13	$149.15	$149.10
Purchase #2	$106.76	11.250%	$118.7705	$118.77	$118.75	$118.80
Purchase #3	$86.35	4.614%	$90.3342	$90.33	$90.35	$90.30
Purchase #4	$79.95	3.150%	$82.4684	$82.47	$82.45	$82.50
Purchase #5	$191.98	4.529%	$200.6748	$200.67	$200.65	$200.70
Purchase #6	$55.50	7.777%	$59.8162	$59.82	$59.80	$59.80
Purchase #7	$55.94	9.128%	$61.0462	$61.05	$61.05	$61.00
7 purchase totals =	$707.75		$762.2422	$762.24	$762.20	$762.20