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	$61.57	10.418%	$67.9844	$67.98	$68.00	$68.00
Purchase #2	$70.77	10.791%	$78.4068	$78.41	$78.40	$78.40
Purchase #3	$202.27	3.414%	$209.1755	$209.18	$209.20	$209.20
Purchase #4	$153.28	9.295%	$167.5274	$167.53	$167.55	$167.50
Purchase #5	$239.78	5.793%	$253.6705	$253.67	$253.65	$253.70
Purchase #6	$221.40	5.587%	$233.7696	$233.77	$233.75	$233.80
Purchase #7	$48.45	13.551%	$55.0155	$55.02	$55.00	$55.00
7 purchase totals =	$997.52		$1,065.5497	$1,065.56	$1,065.55	$1,065.60