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	$152.36	4.812%	$159.6916	$159.69	$159.70	$159.70
Purchase #2	$148.31	3.315%	$153.2265	$153.23	$153.25	$153.20
Purchase #3	$219.73	6.228%	$233.4148	$233.41	$233.40	$233.40
Purchase #4	$178.28	4.428%	$186.1742	$186.17	$186.15	$186.20
Purchase #5	$101.41	10.408%	$111.9648	$111.96	$111.95	$112.00
Purchase #6	$50.34	13.788%	$57.2809	$57.28	$57.30	$57.30
Purchase #7	$73.93	11.546%	$82.466	$82.47	$82.45	$82.50
7 purchase totals =	$924.36		$984.2188	$984.21	$984.20	$984.30