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	$228.87	7.401%	$245.8087	$245.81	$245.80	$245.80
Purchase #2	$20.50	4.726%	$21.4688	$21.47	$21.45	$21.50
Purchase #3	$221.33	8.134%	$239.333	$239.33	$239.35	$239.30
Purchase #4	$88.71	10.279%	$97.8285	$97.83	$97.85	$97.80
Purchase #5	$70.80	10.645%	$78.3367	$78.34	$78.35	$78.30
Purchase #6	$154.39	11.322%	$171.87	$171.87	$171.85	$171.90
Purchase #7	$164.74	10.156%	$181.471	$181.47	$181.45	$181.50
7 purchase totals =	$949.34		$1,036.1167	$1,036.12	$1,036.10	$1,036.10