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	$59.39	4.666%	$62.1611	$62.16	$62.15	$62.20
Purchase #2	$109.36	12.795%	$123.3526	$123.35	$123.35	$123.40
Purchase #3	$62.99	12.799%	$71.0521	$71.05	$71.05	$71.10
Purchase #4	$240.86	11.849%	$269.3995	$269.40	$269.40	$269.40
Purchase #5	$96.25	10.294%	$106.158	$106.16	$106.15	$106.20
Purchase #6	$40.91	10.102%	$45.0427	$45.04	$45.05	$45.00
Purchase #7	$225.31	10.637%	$249.2762	$249.28	$249.30	$249.30
7 purchase totals =	$835.07		$926.4422	$926.44	$926.45	$926.60