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	$118.34	7.513%	$127.2309	$127.23	$127.25	$127.20
Purchase #2	$64.73	9.483%	$70.8683	$70.87	$70.85	$70.90
Purchase #3	$167.91	8.852%	$182.7734	$182.77	$182.75	$182.80
Purchase #4	$44.86	5.799%	$47.4614	$47.46	$47.45	$47.50
Purchase #5	$224.29	4.773%	$234.9954	$235.00	$235.00	$235.00
Purchase #6	$168.47	10.320%	$185.8561	$185.86	$185.85	$185.90
Purchase #7	$232.25	4.551%	$242.8197	$242.82	$242.80	$242.80
7 purchase totals =	$1,020.85		$1,092.0052	$1,092.01	$1,091.95	$1,092.10