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	$66.41	7.320%	$71.2712	$71.27	$71.25	$71.30
Purchase #2	$94.66	6.718%	$101.0193	$101.02	$101.00	$101.00
Purchase #3	$98.87	12.357%	$111.0874	$111.09	$111.10	$111.10
Purchase #4	$27.44	6.807%	$29.3078	$29.31	$29.30	$29.30
Purchase #5	$101.79	12.199%	$114.2074	$114.21	$114.20	$114.20
Purchase #6	$13.78	9.568%	$15.0985	$15.10	$15.10	$15.10
Purchase #7	$7.65	3.556%	$7.922	$7.92	$7.90	$7.90
7 purchase totals =	$410.60		$449.9136	$449.92	$449.85	$449.90