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	$66.56	6.513%	$70.8951	$70.90	$70.90	$70.90
Purchase #2	$137.70	13.351%	$156.0843	$156.08	$156.10	$156.10
Purchase #3	$234.26	3.204%	$241.7657	$241.77	$241.75	$241.80
Purchase #4	$98.59	11.492%	$109.92	$109.92	$109.90	$109.90
Purchase #5	$161.67	11.441%	$180.1667	$180.17	$180.15	$180.20
Purchase #6	$119.75	6.852%	$127.9553	$127.96	$127.95	$128.00
Purchase #7	$169.52	9.646%	$185.8719	$185.87	$185.85	$185.90
7 purchase totals =	$988.05		$1,072.6590	$1,072.67	$1,072.60	$1,072.80