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	$53.28	12.290%	$59.8281	$59.83	$59.85	$59.80
Purchase #2	$74.73	9.259%	$81.6493	$81.65	$81.65	$81.60
Purchase #3	$150.31	7.828%	$162.0763	$162.08	$162.10	$162.10
Purchase #4	$53.48	13.839%	$60.8811	$60.88	$60.90	$60.90
Purchase #5	$131.36	8.795%	$142.9131	$142.91	$142.90	$142.90
Purchase #6	$233.44	4.501%	$243.9471	$243.95	$243.95	$243.90
Purchase #7	$248.28	4.111%	$258.4868	$258.49	$258.50	$258.50
7 purchase totals =	$944.88		$1,009.7818	$1,009.79	$1,009.85	$1,009.70