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	$123.75	13.222%	$140.1122	$140.11	$140.10	$140.10
Purchase #2	$93.33	8.274%	$101.0521	$101.05	$101.05	$101.10
Purchase #3	$81.78	6.202%	$86.852	$86.85	$86.85	$86.90
Purchase #4	$165.62	5.310%	$174.4144	$174.41	$174.40	$174.40
Purchase #5	$204.45	4.618%	$213.8915	$213.89	$213.90	$213.90
Purchase #6	$244.61	8.113%	$264.4552	$264.46	$264.45	$264.50
Purchase #7	$156.83	8.810%	$170.6467	$170.65	$170.65	$170.60
7 purchase totals =	$1,070.37		$1,151.4241	$1,151.42	$1,151.40	$1,151.50