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	$113.88	4.660%	$119.1868	$119.19	$119.20	$119.20
Purchase #2	$64.86	8.693%	$70.4983	$70.50	$70.50	$70.50
Purchase #3	$52.52	13.371%	$59.5424	$59.54	$59.55	$59.50
Purchase #4	$165.33	12.821%	$186.527	$186.53	$186.55	$186.50
Purchase #5	$191.41	10.501%	$211.51	$211.51	$211.50	$211.50
Purchase #6	$96.54	10.546%	$106.7211	$106.72	$106.70	$106.70
Purchase #7	$239.39	9.387%	$261.8615	$261.86	$261.85	$261.90
7 purchase totals =	$923.93		$1,015.8471	$1,015.85	$1,015.85	$1,015.80