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	$160.88	3.732%	$166.884	$166.88	$166.90	$166.90
Purchase #2	$219.90	5.182%	$231.2952	$231.30	$231.30	$231.30
Purchase #3	$110.27	4.500%	$115.2322	$115.23	$115.25	$115.20
Purchase #4	$111.82	10.403%	$123.4526	$123.45	$123.45	$123.50
Purchase #5	$195.79	13.657%	$222.529	$222.53	$222.55	$222.50
Purchase #6	$76.64	9.543%	$83.9538	$83.95	$83.95	$84.00
Purchase #7	$187.42	12.829%	$211.4641	$211.46	$211.45	$211.50
7 purchase totals =	$1,062.72		$1,154.8109	$1,154.80	$1,154.85	$1,154.90