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	$98.45	7.143%	$105.4823	$105.48	$105.50	$105.50
Purchase #2	$94.73	4.698%	$99.1804	$99.18	$99.20	$99.20
Purchase #3	$27.85	4.187%	$29.0161	$29.02	$29.00	$29.00
Purchase #4	$161.43	7.223%	$173.0901	$173.09	$173.10	$173.10
Purchase #5	$72.80	6.406%	$77.4636	$77.46	$77.45	$77.50
Purchase #6	$96.53	7.109%	$103.3923	$103.39	$103.40	$103.40
Purchase #7	$231.49	13.501%	$262.7435	$262.74	$262.75	$262.70
7 purchase totals =	$783.28		$850.3683	$850.36	$850.40	$850.40