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	$133.47	13.609%	$151.6339	$151.63	$151.65	$151.60
Purchase #2	$38.27	12.250%	$42.9581	$42.96	$42.95	$43.00
Purchase #3	$206.74	13.850%	$235.3735	$235.37	$235.35	$235.40
Purchase #4	$245.28	8.103%	$265.155	$265.16	$265.15	$265.20
Purchase #5	$59.90	7.437%	$64.3548	$64.35	$64.35	$64.40
Purchase #6	$25.64	7.402%	$27.5379	$27.54	$27.55	$27.50
Purchase #7	$119.55	7.362%	$128.3513	$128.35	$128.35	$128.40
7 purchase totals =	$828.85		$915.3645	$915.36	$915.35	$915.50