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	$86.27	3.241%	$89.066	$89.07	$89.05	$89.10
Purchase #2	$152.63	3.641%	$158.1873	$158.19	$158.20	$158.20
Purchase #3	$230.78	5.536%	$243.556	$243.56	$243.55	$243.60
Purchase #4	$82.83	3.818%	$85.9924	$85.99	$86.00	$86.00
Purchase #5	$101.56	4.413%	$106.0418	$106.04	$106.05	$106.00
Purchase #6	$168.80	4.361%	$176.1614	$176.16	$176.15	$176.20
Purchase #7	$166.86	12.342%	$187.4539	$187.45	$187.45	$187.50
7 purchase totals =	$989.73		$1,046.4588	$1,046.46	$1,046.45	$1,046.60