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	$217.64	12.460%	$244.7579	$244.76	$244.75	$244.80
Purchase #2	$19.39	4.601%	$20.2821	$20.28	$20.30	$20.30
Purchase #3	$125.95	8.708%	$136.9177	$136.92	$136.90	$136.90
Purchase #4	$68.39	4.505%	$71.471	$71.47	$71.45	$71.50
Purchase #5	$218.88	13.752%	$248.9804	$248.98	$249.00	$249.00
Purchase #6	$156.66	5.536%	$165.3327	$165.33	$165.35	$165.30
Purchase #7	$237.40	9.301%	$259.4806	$259.48	$259.50	$259.50
7 purchase totals =	$1,044.31		$1,147.2224	$1,147.22	$1,147.25	$1,147.30