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	$110.64	11.386%	$123.2375	$123.24	$123.25	$123.20
Purchase #2	$160.56	9.628%	$176.0187	$176.02	$176.00	$176.00
Purchase #3	$119.59	4.147%	$124.5494	$124.55	$124.55	$124.50
Purchase #4	$99.32	5.791%	$105.0716	$105.07	$105.05	$105.10
Purchase #5	$140.56	11.258%	$156.3842	$156.38	$156.40	$156.40
Purchase #6	$239.72	13.503%	$272.0894	$272.09	$272.10	$272.10
Purchase #7	$46.31	13.129%	$52.39	$52.39	$52.40	$52.40
7 purchase totals =	$916.70		$1,009.7408	$1,009.74	$1,009.75	$1,009.70