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	$50.45	11.482%	$56.2427	$56.24	$56.25	$56.20
Purchase #2	$97.90	12.172%	$109.8164	$109.82	$109.80	$109.80
Purchase #3	$73.33	11.500%	$81.763	$81.76	$81.75	$81.80
Purchase #4	$228.76	5.631%	$241.6415	$241.64	$241.65	$241.60
Purchase #5	$165.96	6.519%	$176.7789	$176.78	$176.80	$176.80
Purchase #6	$166.56	5.102%	$175.0579	$175.06	$175.05	$175.10
Purchase #7	$242.33	4.666%	$253.6371	$253.64	$253.65	$253.60
7 purchase totals =	$1,025.29		$1,094.9375	$1,094.94	$1,094.95	$1,094.90