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	$67.30	10.764%	$74.5442	$74.54	$74.55	$74.50
Purchase #2	$245.54	9.513%	$268.8982	$268.90	$268.90	$268.90
Purchase #3	$211.45	12.753%	$238.4162	$238.42	$238.40	$238.40
Purchase #4	$43.51	5.447%	$45.88	$45.88	$45.90	$45.90
Purchase #5	$19.80	13.345%	$22.4423	$22.44	$22.45	$22.40
Purchase #6	$204.67	13.222%	$231.7315	$231.73	$231.75	$231.70
Purchase #7	$153.89	13.464%	$174.6097	$174.61	$174.60	$174.60
7 purchase totals =	$946.16		$1,056.5221	$1,056.52	$1,056.55	$1,056.40