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	$102.66	7.111%	$109.9602	$109.96	$109.95	$110.00
Purchase #2	$59.38	9.118%	$64.7943	$64.79	$64.80	$64.80
Purchase #3	$21.31	7.530%	$22.9146	$22.91	$22.90	$22.90
Purchase #4	$128.29	13.756%	$145.9376	$145.94	$145.95	$145.90
Purchase #5	$106.68	5.860%	$112.9314	$112.93	$112.95	$112.90
Purchase #6	$165.96	11.725%	$185.4188	$185.42	$185.40	$185.40
Purchase #7	$35.97	12.266%	$40.3821	$40.38	$40.40	$40.40
7 purchase totals =	$620.25		$682.3390	$682.33	$682.35	$682.30