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	$22.33	10.578%	$24.6921	$24.69	$24.70	$24.70
Purchase #2	$155.96	7.516%	$167.682	$167.68	$167.70	$167.70
Purchase #3	$10.57	7.796%	$11.394	$11.39	$11.40	$11.40
Purchase #4	$88.82	10.538%	$98.1799	$98.18	$98.20	$98.20
Purchase #5	$70.34	11.544%	$78.46	$78.46	$78.45	$78.50
Purchase #6	$79.80	3.286%	$82.4222	$82.42	$82.40	$82.40
Purchase #7	$10.46	11.125%	$11.6237	$11.62	$11.60	$11.60
7 purchase totals =	$438.28		$474.4539	$474.44	$474.45	$474.50