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	$57.31	11.610%	$63.9637	$63.96	$63.95	$64.00
Purchase #2	$158.33	13.773%	$180.1368	$180.14	$180.15	$180.10
Purchase #3	$228.85	13.289%	$259.2619	$259.26	$259.25	$259.30
Purchase #4	$233.43	12.808%	$263.3277	$263.33	$263.35	$263.30
Purchase #5	$189.92	12.360%	$213.3941	$213.39	$213.40	$213.40
Purchase #6	$60.74	8.118%	$65.6709	$65.67	$65.65	$65.70
Purchase #7	$33.54	11.736%	$37.4763	$37.48	$37.50	$37.50
7 purchase totals =	$962.12		$1,083.2314	$1,083.23	$1,083.25	$1,083.30