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	$112.44	7.457%	$120.8247	$120.82	$120.80	$120.80
Purchase #2	$155.60	11.304%	$173.189	$173.19	$173.20	$173.20
Purchase #3	$70.62	8.245%	$76.4426	$76.44	$76.45	$76.40
Purchase #4	$211.28	9.489%	$231.3284	$231.33	$231.35	$231.30
Purchase #5	$176.78	4.805%	$185.2743	$185.27	$185.25	$185.30
Purchase #6	$133.61	9.614%	$146.4553	$146.46	$146.45	$146.50
Purchase #7	$153.69	7.216%	$164.7803	$164.78	$164.80	$164.80
7 purchase totals =	$1,014.02		$1,098.2946	$1,098.29	$1,098.30	$1,098.30