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	$36.89	13.269%	$41.7849	$41.78	$41.80	$41.80
Purchase #2	$195.33	13.356%	$221.4183	$221.42	$221.40	$221.40
Purchase #3	$76.89	6.806%	$82.1231	$82.12	$82.10	$82.10
Purchase #4	$247.74	10.349%	$273.3786	$273.38	$273.40	$273.40
Purchase #5	$19.54	6.374%	$20.7855	$20.79	$20.80	$20.80
Purchase #6	$163.31	10.267%	$180.077	$180.08	$180.10	$180.10
Purchase #7	$219.68	3.628%	$227.65	$227.65	$227.65	$227.70
7 purchase totals =	$959.38		$1,047.2174	$1,047.22	$1,047.25	$1,047.30