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	$89.79	13.152%	$101.5992	$101.60	$101.60	$101.60
Purchase #2	$195.82	13.754%	$222.7531	$222.75	$222.75	$222.80
Purchase #3	$182.42	9.396%	$199.5602	$199.56	$199.55	$199.60
Purchase #4	$89.97	10.221%	$99.1658	$99.17	$99.15	$99.20
Purchase #5	$167.59	12.375%	$188.3293	$188.33	$188.35	$188.30
Purchase #6	$55.46	6.826%	$59.2457	$59.25	$59.25	$59.20
Purchase #7	$238.38	13.150%	$269.727	$269.73	$269.75	$269.70
7 purchase totals =	$1,019.43		$1,140.3803	$1,140.39	$1,140.40	$1,140.40