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	$120.39	3.710%	$124.8565	$124.86	$124.85	$124.90
Purchase #2	$115.37	3.793%	$119.746	$119.75	$119.75	$119.70
Purchase #3	$204.86	4.573%	$214.2282	$214.23	$214.25	$214.20
Purchase #4	$110.70	11.145%	$123.0375	$123.04	$123.05	$123.00
Purchase #5	$168.43	12.786%	$189.9655	$189.97	$189.95	$190.00
Purchase #6	$47.39	7.261%	$50.831	$50.83	$50.85	$50.80
Purchase #7	$164.76	13.769%	$187.4458	$187.45	$187.45	$187.40
7 purchase totals =	$931.90		$1,010.1105	$1,010.13	$1,010.15	$1,010.00