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	$96.61	7.560%	$103.9137	$103.91	$103.90	$103.90
Purchase #2	$220.94	9.638%	$242.2342	$242.23	$242.25	$242.20
Purchase #3	$45.41	6.360%	$48.2981	$48.30	$48.30	$48.30
Purchase #4	$107.79	9.501%	$118.0311	$118.03	$118.05	$118.00
Purchase #5	$198.40	9.119%	$216.4921	$216.49	$216.50	$216.50
Purchase #6	$53.66	5.816%	$56.7809	$56.78	$56.80	$56.80
Purchase #7	$219.67	3.725%	$227.8527	$227.85	$227.85	$227.90
7 purchase totals =	$942.48		$1,013.6028	$1,013.59	$1,013.65	$1,013.60