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	$151.71	5.151%	$159.5246	$159.52	$159.50	$159.50
Purchase #2	$243.33	6.695%	$259.6209	$259.62	$259.60	$259.60
Purchase #3	$165.46	3.792%	$171.7342	$171.73	$171.75	$171.70
Purchase #4	$70.77	12.739%	$79.7854	$79.79	$79.80	$79.80
Purchase #5	$73.57	6.251%	$78.1689	$78.17	$78.15	$78.20
Purchase #6	$141.26	9.606%	$154.8294	$154.83	$154.85	$154.80
Purchase #7	$51.55	8.437%	$55.8993	$55.90	$55.90	$55.90
7 purchase totals =	$897.65		$959.5627	$959.56	$959.55	$959.50