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	$76.93	7.467%	$82.6744	$82.67	$82.65	$82.70
Purchase #2	$188.56	6.339%	$200.5128	$200.51	$200.50	$200.50
Purchase #3	$115.60	4.514%	$120.8182	$120.82	$120.80	$120.80
Purchase #4	$207.36	6.832%	$221.5268	$221.53	$221.55	$221.50
Purchase #5	$54.77	13.739%	$62.2949	$62.29	$62.30	$62.30
Purchase #6	$233.77	8.574%	$253.8134	$253.81	$253.80	$253.80
Purchase #7	$185.45	13.839%	$211.1144	$211.11	$211.10	$211.10
7 purchase totals =	$1,062.44		$1,152.7549	$1,152.74	$1,152.70	$1,152.70