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	$43.90	5.852%	$46.469	$46.47	$46.45	$46.50
Purchase #2	$136.45	12.290%	$153.2197	$153.22	$153.20	$153.20
Purchase #3	$155.43	4.633%	$162.6311	$162.63	$162.65	$162.60
Purchase #4	$78.76	8.213%	$85.2286	$85.23	$85.25	$85.20
Purchase #5	$180.31	10.874%	$199.9169	$199.92	$199.90	$199.90
Purchase #6	$209.95	4.744%	$219.91	$219.91	$219.90	$219.90
Purchase #7	$205.36	3.345%	$212.2293	$212.23	$212.25	$212.20
7 purchase totals =	$1,010.16		$1,079.6046	$1,079.61	$1,079.60	$1,079.50