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	$125.25	8.677%	$136.1179	$136.12	$136.10	$136.10
Purchase #2	$142.55	4.126%	$148.4316	$148.43	$148.45	$148.40
Purchase #3	$145.86	4.308%	$152.1436	$152.14	$152.15	$152.10
Purchase #4	$218.86	5.435%	$230.755	$230.76	$230.75	$230.80
Purchase #5	$74.88	4.471%	$78.2279	$78.23	$78.25	$78.20
Purchase #6	$197.28	13.130%	$223.1829	$223.18	$223.20	$223.20
Purchase #7	$42.84	3.693%	$44.4221	$44.42	$44.40	$44.40
7 purchase totals =	$947.52		$1,013.2810	$1,013.28	$1,013.30	$1,013.20