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	$117.39	8.432%	$127.2883	$127.29	$127.30	$127.30
Purchase #2	$94.77	11.564%	$105.7292	$105.73	$105.75	$105.70
Purchase #3	$73.84	11.205%	$82.1138	$82.11	$82.10	$82.10
Purchase #4	$157.98	12.852%	$178.2836	$178.28	$178.30	$178.30
Purchase #5	$219.93	4.339%	$229.4728	$229.47	$229.45	$229.50
Purchase #6	$109.70	4.367%	$114.4906	$114.49	$114.50	$114.50
Purchase #7	$23.36	7.841%	$25.1917	$25.19	$25.20	$25.20
7 purchase totals =	$796.97		$862.5700	$862.56	$862.60	$862.60