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	$195.77	8.788%	$212.9743	$212.97	$212.95	$213.00
Purchase #2	$119.51	7.641%	$128.6418	$128.64	$128.65	$128.60
Purchase #3	$200.56	11.121%	$222.8643	$222.86	$222.85	$222.90
Purchase #4	$162.33	12.287%	$182.2755	$182.28	$182.30	$182.30
Purchase #5	$80.85	13.432%	$91.7098	$91.71	$91.70	$91.70
Purchase #6	$25.72	7.459%	$27.6385	$27.64	$27.65	$27.60
Purchase #7	$31.59	12.211%	$35.4475	$35.45	$35.45	$35.40
7 purchase totals =	$816.33		$901.5517	$901.55	$901.55	$901.50