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	$96.51	5.139%	$101.4696	$101.47	$101.45	$101.50
Purchase #2	$37.61	3.348%	$38.8692	$38.87	$38.85	$38.90
Purchase #3	$92.47	9.760%	$101.4951	$101.50	$101.50	$101.50
Purchase #4	$130.66	4.316%	$136.2993	$136.30	$136.30	$136.30
Purchase #5	$245.99	5.134%	$258.6191	$258.62	$258.60	$258.60
Purchase #6	$99.92	13.751%	$113.66	$113.66	$113.65	$113.70
Purchase #7	$165.45	4.280%	$172.5313	$172.53	$172.55	$172.50
7 purchase totals =	$868.61		$922.9436	$922.95	$922.90	$923.00