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	$111.64	10.160%	$122.9826	$122.98	$123.00	$123.00
Purchase #2	$228.84	7.448%	$245.884	$245.88	$245.90	$245.90
Purchase #3	$55.88	5.602%	$59.0104	$59.01	$59.00	$59.00
Purchase #4	$85.34	8.471%	$92.5692	$92.57	$92.55	$92.60
Purchase #5	$173.97	6.114%	$184.6065	$184.61	$184.60	$184.60
Purchase #6	$208.39	9.169%	$227.4973	$227.50	$227.50	$227.50
Purchase #7	$99.29	10.567%	$109.782	$109.78	$109.80	$109.80
7 purchase totals =	$963.35		$1,042.3320	$1,042.33	$1,042.35	$1,042.40