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	$43.34	7.498%	$46.5896	$46.59	$46.60	$46.60
Purchase #2	$86.74	3.257%	$89.5651	$89.57	$89.55	$89.60
Purchase #3	$22.93	11.781%	$25.6314	$25.63	$25.65	$25.60
Purchase #4	$166.33	11.175%	$184.9174	$184.92	$184.90	$184.90
Purchase #5	$201.44	5.376%	$212.2694	$212.27	$212.25	$212.30
Purchase #6	$37.72	13.367%	$42.762	$42.76	$42.75	$42.80
Purchase #7	$168.41	12.487%	$189.4394	$189.44	$189.45	$189.40
7 purchase totals =	$726.91		$791.1743	$791.18	$791.15	$791.20