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	$101.86	7.751%	$109.7552	$109.76	$109.75	$109.80
Purchase #2	$106.28	12.527%	$119.5937	$119.59	$119.60	$119.60
Purchase #3	$240.53	11.772%	$268.8452	$268.85	$268.85	$268.80
Purchase #4	$40.61	4.652%	$42.4992	$42.50	$42.50	$42.50
Purchase #5	$173.83	6.814%	$185.6748	$185.67	$185.65	$185.70
Purchase #6	$29.31	4.769%	$30.7078	$30.71	$30.70	$30.70
Purchase #7	$209.93	6.366%	$223.2941	$223.29	$223.30	$223.30
7 purchase totals =	$902.35		$980.3700	$980.37	$980.35	$980.40