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	$53.54	10.714%	$59.2763	$59.28	$59.30	$59.30
Purchase #2	$81.96	7.459%	$88.0734	$88.07	$88.05	$88.10
Purchase #3	$167.99	8.595%	$182.4287	$182.43	$182.45	$182.40
Purchase #4	$184.75	8.608%	$200.6533	$200.65	$200.65	$200.70
Purchase #5	$162.85	13.874%	$185.4438	$185.44	$185.45	$185.40
Purchase #6	$24.90	11.599%	$27.7882	$27.79	$27.80	$27.80
Purchase #7	$186.80	12.115%	$209.4308	$209.43	$209.45	$209.40
7 purchase totals =	$862.79		$953.0945	$953.09	$953.15	$953.10