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	$47.33	10.795%	$52.4393	$52.44	$52.45	$52.40
Purchase #2	$226.53	8.127%	$244.9401	$244.94	$244.95	$244.90
Purchase #3	$78.78	8.685%	$85.622	$85.62	$85.60	$85.60
Purchase #4	$228.52	11.525%	$254.8569	$254.86	$254.85	$254.90
Purchase #5	$103.83	5.476%	$109.5157	$109.52	$109.50	$109.50
Purchase #6	$50.40	5.649%	$53.2471	$53.25	$53.25	$53.20
Purchase #7	$244.96	13.119%	$277.0963	$277.10	$277.10	$277.10
7 purchase totals =	$980.35		$1,077.7174	$1,077.73	$1,077.70	$1,077.60