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	$94.86	11.175%	$105.4606	$105.46	$105.45	$105.50
Purchase #2	$39.93	10.488%	$44.1179	$44.12	$44.10	$44.10
Purchase #3	$64.66	13.259%	$73.2333	$73.23	$73.25	$73.20
Purchase #4	$184.90	11.114%	$205.4498	$205.45	$205.45	$205.40
Purchase #5	$114.87	12.574%	$129.3138	$129.31	$129.30	$129.30
Purchase #6	$246.66	7.188%	$264.3899	$264.39	$264.40	$264.40
Purchase #7	$158.84	8.547%	$172.4161	$172.42	$172.40	$172.40
7 purchase totals =	$904.72		$994.3814	$994.38	$994.35	$994.30