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	$147.83	11.787%	$165.2547	$165.25	$165.25	$165.30
Purchase #2	$37.98	9.686%	$41.6587	$41.66	$41.65	$41.70
Purchase #3	$31.65	12.772%	$35.6923	$35.69	$35.70	$35.70
Purchase #4	$185.49	8.321%	$200.9246	$200.92	$200.90	$200.90
Purchase #5	$202.52	8.586%	$219.9084	$219.91	$219.90	$219.90
Purchase #6	$241.54	8.181%	$261.3004	$261.30	$261.30	$261.30
Purchase #7	$121.77	5.829%	$128.868	$128.87	$128.85	$128.90
7 purchase totals =	$968.78		$1,053.6071	$1,053.60	$1,053.55	$1,053.70