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	$128.61	5.745%	$135.9986	$136.00	$136.00	$136.00
Purchase #2	$238.51	6.681%	$254.4449	$254.44	$254.45	$254.40
Purchase #3	$137.91	4.152%	$143.636	$143.64	$143.65	$143.60
Purchase #4	$86.66	6.851%	$92.5971	$92.60	$92.60	$92.60
Purchase #5	$159.33	3.363%	$164.6883	$164.69	$164.70	$164.70
Purchase #6	$210.45	6.141%	$223.3737	$223.37	$223.35	$223.40
Purchase #7	$88.31	12.869%	$99.6746	$99.67	$99.65	$99.70
7 purchase totals =	$1,049.78		$1,114.4132	$1,114.41	$1,114.40	$1,114.40