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	$158.75	8.376%	$172.0469	$172.05	$172.05	$172.00
Purchase #2	$49.59	7.590%	$53.3539	$53.35	$53.35	$53.40
Purchase #3	$96.45	13.317%	$109.2942	$109.29	$109.30	$109.30
Purchase #4	$212.97	8.426%	$230.9149	$230.91	$230.90	$230.90
Purchase #5	$50.30	7.627%	$54.1364	$54.14	$54.15	$54.10
Purchase #6	$133.34	3.287%	$137.7229	$137.72	$137.70	$137.70
Purchase #7	$220.55	12.397%	$247.8916	$247.89	$247.90	$247.90
7 purchase totals =	$921.95		$1,005.3608	$1,005.35	$1,005.35	$1,005.30