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	$167.44	9.282%	$182.9818	$182.98	$183.00	$183.00
Purchase #2	$250.51	3.104%	$258.2858	$258.29	$258.30	$258.30
Purchase #3	$76.77	11.178%	$85.3514	$85.35	$85.35	$85.40
Purchase #4	$219.53	9.109%	$239.527	$239.53	$239.55	$239.50
Purchase #5	$105.60	6.168%	$112.1134	$112.11	$112.10	$112.10
Purchase #6	$119.76	7.163%	$128.3384	$128.34	$128.35	$128.30
Purchase #7	$121.98	7.330%	$130.9211	$130.92	$130.90	$130.90
7 purchase totals =	$1,061.59		$1,137.5189	$1,137.52	$1,137.55	$1,137.50