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	$94.50	11.585%	$105.4478	$105.45	$105.45	$105.40
Purchase #2	$52.58	5.823%	$55.6417	$55.64	$55.65	$55.60
Purchase #3	$5.49	12.734%	$6.1891	$6.19	$6.20	$6.20
Purchase #4	$78.57	10.361%	$86.7106	$86.71	$86.70	$86.70
Purchase #5	$53.58	10.301%	$59.0993	$59.10	$59.10	$59.10
Purchase #6	$115.98	8.608%	$125.9636	$125.96	$125.95	$126.00
Purchase #7	$209.64	6.787%	$223.8683	$223.87	$223.85	$223.90
7 purchase totals =	$610.34		$662.9204	$662.92	$662.90	$662.90