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	$149.74	4.405%	$156.336	$156.34	$156.35	$156.30
Purchase #2	$179.98	5.780%	$190.3828	$190.38	$190.40	$190.40
Purchase #3	$126.59	11.439%	$141.0706	$141.07	$141.05	$141.10
Purchase #4	$230.44	7.526%	$247.7829	$247.78	$247.80	$247.80
Purchase #5	$96.69	7.612%	$104.05	$104.05	$104.05	$104.10
Purchase #6	$124.27	12.489%	$139.7901	$139.79	$139.80	$139.80
Purchase #7	$161.33	4.140%	$168.0091	$168.01	$168.00	$168.00
7 purchase totals =	$1,069.04		$1,147.4215	$1,147.42	$1,147.45	$1,147.50