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	$145.64	7.472%	$156.5222	$156.52	$156.50	$156.50
Purchase #2	$156.64	6.107%	$166.206	$166.21	$166.20	$166.20
Purchase #3	$231.40	9.867%	$254.2322	$254.23	$254.25	$254.20
Purchase #4	$93.86	6.431%	$99.8961	$99.90	$99.90	$99.90
Purchase #5	$131.41	8.414%	$142.4668	$142.47	$142.45	$142.50
Purchase #6	$190.31	11.842%	$212.8465	$212.85	$212.85	$212.80
Purchase #7	$149.25	4.331%	$155.714	$155.71	$155.70	$155.70
7 purchase totals =	$1,098.51		$1,187.8838	$1,187.89	$1,187.85	$1,187.80