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	$85.37	6.779%	$91.1572	$91.16	$91.15	$91.20
Purchase #2	$226.73	3.581%	$234.8492	$234.85	$234.85	$234.80
Purchase #3	$56.46	4.773%	$59.1548	$59.15	$59.15	$59.20
Purchase #4	$135.60	3.540%	$140.4002	$140.40	$140.40	$140.40
Purchase #5	$13.40	9.390%	$14.6583	$14.66	$14.65	$14.70
Purchase #6	$92.31	11.499%	$102.9247	$102.92	$102.90	$102.90
Purchase #7	$215.86	3.488%	$223.3892	$223.39	$223.40	$223.40
7 purchase totals =	$825.73		$866.5336	$866.53	$866.50	$866.60