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	$190.45	4.353%	$198.7403	$198.74	$198.75	$198.70
Purchase #2	$70.63	10.742%	$78.2171	$78.22	$78.20	$78.20
Purchase #3	$163.73	7.816%	$176.5271	$176.53	$176.55	$176.50
Purchase #4	$189.77	10.189%	$209.1057	$209.11	$209.10	$209.10
Purchase #5	$91.89	10.412%	$101.4576	$101.46	$101.45	$101.50
Purchase #6	$143.97	7.277%	$154.4467	$154.45	$154.45	$154.40
Purchase #7	$187.59	13.764%	$213.4099	$213.41	$213.40	$213.40
7 purchase totals =	$1,038.03		$1,131.9044	$1,131.92	$1,131.90	$1,131.80