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	$103.40	5.352%	$108.934	$108.93	$108.95	$108.90
Purchase #2	$72.91	10.236%	$80.3731	$80.37	$80.35	$80.40
Purchase #3	$80.50	13.811%	$91.6179	$91.62	$91.60	$91.60
Purchase #4	$67.46	6.476%	$71.8287	$71.83	$71.85	$71.80
Purchase #5	$104.90	5.368%	$110.531	$110.53	$110.55	$110.50
Purchase #6	$69.86	10.151%	$76.9515	$76.95	$76.95	$77.00
Purchase #7	$205.61	11.404%	$229.0578	$229.06	$229.05	$229.10
7 purchase totals =	$704.64		$769.2940	$769.29	$769.30	$769.30