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	$81.58	13.248%	$92.3877	$92.39	$92.40	$92.40
Purchase #2	$247.92	10.496%	$273.9417	$273.94	$273.95	$273.90
Purchase #3	$62.96	7.576%	$67.7298	$67.73	$67.75	$67.70
Purchase #4	$139.33	8.454%	$151.109	$151.11	$151.10	$151.10
Purchase #5	$241.70	12.265%	$271.3445	$271.34	$271.35	$271.30
Purchase #6	$181.54	6.525%	$193.3855	$193.39	$193.40	$193.40
Purchase #7	$99.69	12.721%	$112.3716	$112.37	$112.35	$112.40
7 purchase totals =	$1,054.72		$1,162.2698	$1,162.27	$1,162.30	$1,162.20