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	$148.40	5.310%	$156.28	$156.28	$156.30	$156.30
Purchase #2	$88.59	4.378%	$92.4685	$92.47	$92.45	$92.50
Purchase #3	$173.93	11.275%	$193.5406	$193.54	$193.55	$193.50
Purchase #4	$57.70	3.608%	$59.7818	$59.78	$59.80	$59.80
Purchase #5	$103.86	12.872%	$117.2289	$117.23	$117.25	$117.20
Purchase #6	$193.39	13.363%	$219.2327	$219.23	$219.25	$219.20
Purchase #7	$72.46	8.471%	$78.5981	$78.60	$78.60	$78.60
7 purchase totals =	$838.33		$917.1306	$917.13	$917.20	$917.10