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	$151.51	3.744%	$157.1825	$157.18	$157.20	$157.20
Purchase #2	$80.27	10.265%	$88.5097	$88.51	$88.50	$88.50
Purchase #3	$162.96	10.215%	$179.6064	$179.61	$179.60	$179.60
Purchase #4	$141.89	7.233%	$152.1529	$152.15	$152.15	$152.20
Purchase #5	$128.69	4.729%	$134.7758	$134.78	$134.80	$134.80
Purchase #6	$60.47	6.386%	$64.3316	$64.33	$64.35	$64.30
Purchase #7	$220.96	6.716%	$235.7997	$235.80	$235.80	$235.80
7 purchase totals =	$946.75		$1,012.3586	$1,012.36	$1,012.40	$1,012.40