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	$30.64	7.217%	$32.8513	$32.85	$32.85	$32.90
Purchase #2	$220.86	13.523%	$250.7269	$250.73	$250.75	$250.70
Purchase #3	$104.46	4.864%	$109.5409	$109.54	$109.55	$109.50
Purchase #4	$148.39	7.483%	$159.494	$159.49	$159.50	$159.50
Purchase #5	$124.33	11.223%	$138.2836	$138.28	$138.30	$138.30
Purchase #6	$60.65	6.167%	$64.3903	$64.39	$64.40	$64.40
Purchase #7	$31.35	7.458%	$33.6881	$33.69	$33.70	$33.70
7 purchase totals =	$720.68		$788.9751	$788.97	$789.05	$789.00