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	$174.37	6.574%	$185.8331	$185.83	$185.85	$185.80
Purchase #2	$44.93	9.294%	$49.1058	$49.11	$49.10	$49.10
Purchase #3	$241.58	3.230%	$249.383	$249.38	$249.40	$249.40
Purchase #4	$219.52	12.826%	$247.6756	$247.68	$247.70	$247.70
Purchase #5	$86.28	3.198%	$89.0392	$89.04	$89.05	$89.00
Purchase #6	$172.78	7.450%	$185.6521	$185.65	$185.65	$185.70
Purchase #7	$64.82	9.382%	$70.9014	$70.90	$70.90	$70.90
7 purchase totals =	$1,004.28		$1,077.5902	$1,077.59	$1,077.65	$1,077.60