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	$172.57	7.827%	$186.0771	$186.08	$186.10	$186.10
Purchase #2	$249.56	13.401%	$283.0035	$283.00	$283.00	$283.00
Purchase #3	$228.55	4.377%	$238.5536	$238.55	$238.55	$238.60
Purchase #4	$99.78	11.749%	$111.5032	$111.50	$111.50	$111.50
Purchase #5	$47.72	12.463%	$53.6673	$53.67	$53.65	$53.70
Purchase #6	$222.60	9.216%	$243.1148	$243.11	$243.10	$243.10
Purchase #7	$66.46	4.701%	$69.5843	$69.58	$69.60	$69.60
7 purchase totals =	$1,087.24		$1,185.5038	$1,185.49	$1,185.50	$1,185.60