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	$141.32	7.648%	$152.1282	$152.13	$152.15	$152.10
Purchase #2	$89.63	7.289%	$96.1631	$96.16	$96.15	$96.20
Purchase #3	$55.96	11.700%	$62.5073	$62.51	$62.50	$62.50
Purchase #4	$62.32	4.559%	$65.1612	$65.16	$65.15	$65.20
Purchase #5	$38.75	12.494%	$43.5914	$43.59	$43.60	$43.60
Purchase #6	$228.95	12.348%	$257.2207	$257.22	$257.20	$257.20
Purchase #7	$185.94	4.427%	$194.1716	$194.17	$194.15	$194.20
7 purchase totals =	$802.87		$870.9435	$870.94	$870.90	$871.00