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	$86.68	11.115%	$96.3145	$96.31	$96.30	$96.30
Purchase #2	$93.51	7.655%	$100.6682	$100.67	$100.65	$100.70
Purchase #3	$211.55	13.668%	$240.4647	$240.46	$240.45	$240.50
Purchase #4	$244.28	11.780%	$273.0562	$273.06	$273.05	$273.10
Purchase #5	$171.64	10.536%	$189.724	$189.72	$189.70	$189.70
Purchase #6	$229.50	5.455%	$242.0192	$242.02	$242.00	$242.00
Purchase #7	$34.86	12.499%	$39.2172	$39.22	$39.20	$39.20
7 purchase totals =	$1,072.02		$1,181.4640	$1,181.46	$1,181.35	$1,181.50