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	$211.40	5.140%	$222.266	$222.27	$222.25	$222.30
Purchase #2	$183.54	11.392%	$204.4489	$204.45	$204.45	$204.40
Purchase #3	$55.33	8.346%	$59.9478	$59.95	$59.95	$59.90
Purchase #4	$33.60	7.302%	$36.0535	$36.05	$36.05	$36.10
Purchase #5	$47.28	13.434%	$53.6316	$53.63	$53.65	$53.60
Purchase #6	$229.82	7.270%	$246.5279	$246.53	$246.55	$246.50
Purchase #7	$75.89	9.615%	$83.1868	$83.19	$83.20	$83.20
7 purchase totals =	$836.86		$906.0625	$906.07	$906.10	$906.00