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	$43.60	9.572%	$47.7734	$47.77	$47.75	$47.80
Purchase #2	$43.67	4.772%	$45.7539	$45.75	$45.75	$45.80
Purchase #3	$65.25	9.201%	$71.2537	$71.25	$71.25	$71.30
Purchase #4	$168.68	5.687%	$178.2728	$178.27	$178.25	$178.30
Purchase #5	$55.56	12.811%	$62.6778	$62.68	$62.70	$62.70
Purchase #6	$145.97	12.733%	$164.5564	$164.56	$164.55	$164.60
Purchase #7	$174.81	3.316%	$180.6067	$180.61	$180.60	$180.60
7 purchase totals =	$697.54		$750.8947	$750.89	$750.85	$751.10