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	$133.45	13.835%	$151.9128	$151.91	$151.90	$151.90
Purchase #2	$35.36	6.778%	$37.7567	$37.76	$37.75	$37.80
Purchase #3	$119.42	3.421%	$123.5054	$123.51	$123.50	$123.50
Purchase #4	$88.76	3.165%	$91.5693	$91.57	$91.55	$91.60
Purchase #5	$189.33	13.245%	$214.4068	$214.41	$214.40	$214.40
Purchase #6	$37.89	13.562%	$43.0286	$43.03	$43.05	$43.00
Purchase #7	$201.94	4.796%	$211.625	$211.63	$211.65	$211.60
7 purchase totals =	$806.15		$873.8046	$873.82	$873.80	$873.80