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	$195.43	12.771%	$220.3884	$220.39	$220.40	$220.40
Purchase #2	$84.86	13.619%	$96.4171	$96.42	$96.40	$96.40
Purchase #3	$173.45	3.214%	$179.0247	$179.02	$179.00	$179.00
Purchase #4	$96.45	5.141%	$101.4085	$101.41	$101.40	$101.40
Purchase #5	$142.52	9.550%	$156.1307	$156.13	$156.15	$156.10
Purchase #6	$85.57	4.808%	$89.6842	$89.68	$89.70	$89.70
Purchase #7	$184.37	11.610%	$205.7754	$205.78	$205.80	$205.80
7 purchase totals =	$962.65		$1,048.8290	$1,048.83	$1,048.85	$1,048.80