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	$124.68	5.397%	$131.409	$131.41	$131.40	$131.40
Purchase #2	$25.72	9.855%	$28.2547	$28.25	$28.25	$28.30
Purchase #3	$49.35	9.813%	$54.1927	$54.19	$54.20	$54.20
Purchase #4	$175.48	11.345%	$195.3882	$195.39	$195.40	$195.40
Purchase #5	$53.84	10.770%	$59.6386	$59.64	$59.65	$59.60
Purchase #6	$86.30	11.650%	$96.354	$96.35	$96.35	$96.40
Purchase #7	$140.39	5.129%	$147.5906	$147.59	$147.60	$147.60
7 purchase totals =	$655.76		$712.8278	$712.82	$712.85	$712.90