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	$191.71	8.715%	$208.4175	$208.42	$208.40	$208.40
Purchase #2	$244.75	3.421%	$253.1229	$253.12	$253.10	$253.10
Purchase #3	$171.40	10.164%	$188.8211	$188.82	$188.80	$188.80
Purchase #4	$105.88	3.479%	$109.5636	$109.56	$109.55	$109.60
Purchase #5	$233.27	5.242%	$245.498	$245.50	$245.50	$245.50
Purchase #6	$64.46	4.298%	$67.2305	$67.23	$67.25	$67.20
Purchase #7	$131.31	11.205%	$146.0233	$146.02	$146.00	$146.00
7 purchase totals =	$1,142.78		$1,218.6769	$1,218.67	$1,218.60	$1,218.60