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	$194.91	11.221%	$216.7809	$216.78	$216.80	$216.80
Purchase #2	$219.71	7.765%	$236.7705	$236.77	$236.75	$236.80
Purchase #3	$150.61	10.590%	$166.5596	$166.56	$166.55	$166.60
Purchase #4	$18.62	8.872%	$20.272	$20.27	$20.25	$20.30
Purchase #5	$84.37	6.599%	$89.9376	$89.94	$89.95	$89.90
Purchase #6	$34.77	13.266%	$39.3826	$39.38	$39.40	$39.40
Purchase #7	$33.34	4.247%	$34.7559	$34.76	$34.75	$34.80
7 purchase totals =	$736.33		$804.4591	$804.46	$804.45	$804.60