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	$96.41	9.864%	$105.9199	$105.92	$105.90	$105.90
Purchase #2	$12.61	11.687%	$14.0837	$14.08	$14.10	$14.10
Purchase #3	$84.41	7.695%	$90.9053	$90.91	$90.90	$90.90
Purchase #4	$171.90	8.770%	$186.9756	$186.98	$187.00	$187.00
Purchase #5	$62.72	9.538%	$68.7022	$68.70	$68.70	$68.70
Purchase #6	$53.55	4.714%	$56.0743	$56.07	$56.05	$56.10
Purchase #7	$228.72	6.631%	$243.8864	$243.89	$243.90	$243.90
7 purchase totals =	$710.32		$766.5474	$766.55	$766.55	$766.60