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	$185.55	7.569%	$199.5943	$199.59	$199.60	$199.60
Purchase #2	$92.69	6.834%	$99.0244	$99.02	$99.00	$99.00
Purchase #3	$67.90	3.252%	$70.1081	$70.11	$70.10	$70.10
Purchase #4	$231.36	10.820%	$256.3932	$256.39	$256.40	$256.40
Purchase #5	$185.73	3.599%	$192.4144	$192.41	$192.40	$192.40
Purchase #6	$156.30	4.156%	$162.7958	$162.80	$162.80	$162.80
Purchase #7	$163.60	5.582%	$172.7322	$172.73	$172.75	$172.70
7 purchase totals =	$1,083.13		$1,153.0624	$1,153.05	$1,153.05	$1,153.00