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	$197.30	12.663%	$222.2841	$222.28	$222.30	$222.30
Purchase #2	$41.98	7.233%	$45.0164	$45.02	$45.00	$45.00
Purchase #3	$43.91	3.346%	$45.3792	$45.38	$45.40	$45.40
Purchase #4	$219.79	5.555%	$231.9993	$232.00	$232.00	$232.00
Purchase #5	$201.50	9.132%	$219.901	$219.90	$219.90	$219.90
Purchase #6	$96.85	12.836%	$109.2817	$109.28	$109.30	$109.30
Purchase #7	$38.59	5.480%	$40.7047	$40.70	$40.70	$40.70
7 purchase totals =	$839.92		$914.5664	$914.56	$914.60	$914.60