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	$168.27	13.735%	$191.3819	$191.38	$191.40	$191.40
Purchase #2	$225.52	3.741%	$233.9567	$233.96	$233.95	$234.00
Purchase #3	$129.45	11.388%	$144.1918	$144.19	$144.20	$144.20
Purchase #4	$50.54	4.250%	$52.688	$52.69	$52.70	$52.70
Purchase #5	$234.31	5.229%	$246.5621	$246.56	$246.55	$246.60
Purchase #6	$156.51	5.646%	$165.3466	$165.35	$165.35	$165.30
Purchase #7	$100.73	9.812%	$110.6136	$110.61	$110.60	$110.60
7 purchase totals =	$1,065.33		$1,144.7407	$1,144.74	$1,144.75	$1,144.80