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	$84.25	11.402%	$93.8562	$93.86	$93.85	$93.90
Purchase #2	$200.56	7.639%	$215.8808	$215.88	$215.90	$215.90
Purchase #3	$165.32	13.416%	$187.4993	$187.50	$187.50	$187.50
Purchase #4	$142.85	4.213%	$148.8683	$148.87	$148.85	$148.90
Purchase #5	$72.78	4.648%	$76.1628	$76.16	$76.15	$76.20
Purchase #6	$36.84	13.652%	$41.8694	$41.87	$41.85	$41.90
Purchase #7	$59.26	3.112%	$61.1042	$61.10	$61.10	$61.10
7 purchase totals =	$761.86		$825.2410	$825.24	$825.20	$825.40