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	$133.83	12.663%	$150.7769	$150.78	$150.80	$150.80
Purchase #2	$119.27	10.345%	$131.6085	$131.61	$131.60	$131.60
Purchase #3	$140.41	6.506%	$149.5451	$149.55	$149.55	$149.50
Purchase #4	$168.66	7.543%	$181.382	$181.38	$181.40	$181.40
Purchase #5	$240.92	9.308%	$263.3448	$263.34	$263.35	$263.30
Purchase #6	$135.28	13.674%	$153.7782	$153.78	$153.80	$153.80
Purchase #7	$203.81	9.462%	$223.0945	$223.09	$223.10	$223.10
7 purchase totals =	$1,142.18		$1,253.5300	$1,253.53	$1,253.60	$1,253.50