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	$109.61	4.642%	$114.6981	$114.70	$114.70	$114.70
Purchase #2	$52.52	12.861%	$59.2746	$59.27	$59.25	$59.30
Purchase #3	$179.59	3.513%	$185.899	$185.90	$185.90	$185.90
Purchase #4	$46.87	4.772%	$49.1066	$49.11	$49.10	$49.10
Purchase #5	$42.55	9.683%	$46.6701	$46.67	$46.65	$46.70
Purchase #6	$221.83	9.595%	$243.1146	$243.11	$243.10	$243.10
Purchase #7	$58.78	5.204%	$61.8389	$61.84	$61.85	$61.80
7 purchase totals =	$711.75		$760.6019	$760.60	$760.55	$760.60