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	$143.91	8.494%	$156.1337	$156.13	$156.15	$156.10
Purchase #2	$73.34	7.190%	$78.6131	$78.61	$78.60	$78.60
Purchase #3	$153.86	5.351%	$162.093	$162.09	$162.10	$162.10
Purchase #4	$224.61	6.188%	$238.5089	$238.51	$238.50	$238.50
Purchase #5	$95.37	8.344%	$103.3277	$103.33	$103.35	$103.30
Purchase #6	$187.50	9.153%	$204.6619	$204.66	$204.65	$204.70
Purchase #7	$196.61	11.588%	$219.3932	$219.39	$219.40	$219.40
7 purchase totals =	$1,075.20		$1,162.7315	$1,162.72	$1,162.75	$1,162.70