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	$91.67	8.686%	$99.6325	$99.63	$99.65	$99.60
Purchase #2	$169.31	7.532%	$182.0624	$182.06	$182.05	$182.10
Purchase #3	$211.42	6.683%	$225.5492	$225.55	$225.55	$225.50
Purchase #4	$59.64	8.111%	$64.4774	$64.48	$64.50	$64.50
Purchase #5	$38.99	6.240%	$41.423	$41.42	$41.40	$41.40
Purchase #6	$167.56	13.627%	$190.3934	$190.39	$190.40	$190.40
Purchase #7	$68.93	6.382%	$73.3291	$73.33	$73.35	$73.30
7 purchase totals =	$807.52		$876.8670	$876.86	$876.90	$876.80