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	$155.82	10.269%	$171.8212	$171.82	$171.80	$171.80
Purchase #2	$131.36	8.774%	$142.8855	$142.89	$142.90	$142.90
Purchase #3	$184.33	7.636%	$198.4054	$198.41	$198.40	$198.40
Purchase #4	$33.99	10.758%	$37.6466	$37.65	$37.65	$37.60
Purchase #5	$161.28	6.673%	$172.0422	$172.04	$172.05	$172.00
Purchase #6	$143.87	3.571%	$149.0076	$149.01	$149.00	$149.00
Purchase #7	$125.79	8.844%	$136.9149	$136.91	$136.90	$136.90
7 purchase totals =	$936.44		$1,008.7234	$1,008.73	$1,008.70	$1,008.60