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	$142.61	9.282%	$155.8471	$155.85	$155.85	$155.80
Purchase #2	$111.51	13.149%	$126.1724	$126.17	$126.15	$126.20
Purchase #3	$168.90	11.582%	$188.462	$188.46	$188.45	$188.50
Purchase #4	$244.43	13.645%	$277.7825	$277.78	$277.80	$277.80
Purchase #5	$43.54	9.305%	$47.5914	$47.59	$47.60	$47.60
Purchase #6	$204.89	11.797%	$229.0609	$229.06	$229.05	$229.10
Purchase #7	$150.98	5.571%	$159.3911	$159.39	$159.40	$159.40
7 purchase totals =	$1,066.86		$1,184.3074	$1,184.30	$1,184.30	$1,184.40