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	$158.68	7.872%	$171.1713	$171.17	$171.15	$171.20
Purchase #2	$20.61	9.180%	$22.502	$22.50	$22.50	$22.50
Purchase #3	$212.62	4.502%	$222.1922	$222.19	$222.20	$222.20
Purchase #4	$18.61	7.780%	$20.0579	$20.06	$20.05	$20.10
Purchase #5	$92.81	7.272%	$99.5591	$99.56	$99.55	$99.60
Purchase #6	$202.84	11.118%	$225.3918	$225.39	$225.40	$225.40
Purchase #7	$29.30	8.355%	$31.748	$31.75	$31.75	$31.70
7 purchase totals =	$735.47		$792.6223	$792.62	$792.60	$792.70