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	$218.31	9.406%	$238.8442	$238.84	$238.85	$238.80
Purchase #2	$107.26	10.567%	$118.5942	$118.59	$118.60	$118.60
Purchase #3	$38.80	10.459%	$42.8581	$42.86	$42.85	$42.90
Purchase #4	$156.37	11.603%	$174.5136	$174.51	$174.50	$174.50
Purchase #5	$230.88	5.338%	$243.2044	$243.20	$243.20	$243.20
Purchase #6	$137.84	9.217%	$150.5447	$150.54	$150.55	$150.50
Purchase #7	$219.50	4.687%	$229.788	$229.79	$229.80	$229.80
7 purchase totals =	$1,108.96		$1,198.3472	$1,198.33	$1,198.35	$1,198.30