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	$150.59	11.250%	$167.5314	$167.53	$167.55	$167.50
Purchase #2	$59.92	3.267%	$61.8776	$61.88	$61.90	$61.90
Purchase #3	$140.95	4.853%	$147.7903	$147.79	$147.80	$147.80
Purchase #4	$78.31	4.433%	$81.7815	$81.78	$81.80	$81.80
Purchase #5	$247.84	9.316%	$270.9288	$270.93	$270.95	$270.90
Purchase #6	$115.86	3.195%	$119.5617	$119.56	$119.55	$119.60
Purchase #7	$220.26	11.485%	$245.5569	$245.56	$245.55	$245.60
7 purchase totals =	$1,013.73		$1,095.0282	$1,095.03	$1,095.10	$1,095.10