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	$91.92	4.528%	$96.0821	$96.08	$96.10	$96.10
Purchase #2	$84.68	10.459%	$93.5367	$93.54	$93.55	$93.50
Purchase #3	$117.95	4.673%	$123.4618	$123.46	$123.45	$123.50
Purchase #4	$238.83	10.129%	$263.0211	$263.02	$263.00	$263.00
Purchase #5	$167.94	13.678%	$190.9108	$190.91	$190.90	$190.90
Purchase #6	$67.52	5.730%	$71.3889	$71.39	$71.40	$71.40
Purchase #7	$185.46	5.446%	$195.5602	$195.56	$195.55	$195.60
7 purchase totals =	$954.30		$1,033.9616	$1,033.96	$1,033.95	$1,034.00