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	$147.62	3.419%	$152.6671	$152.67	$152.65	$152.70
Purchase #2	$35.28	6.191%	$37.4642	$37.46	$37.45	$37.50
Purchase #3	$227.95	12.421%	$256.2637	$256.26	$256.25	$256.30
Purchase #4	$83.26	9.728%	$91.3595	$91.36	$91.35	$91.40
Purchase #5	$59.85	11.687%	$66.8447	$66.84	$66.85	$66.80
Purchase #6	$194.61	7.866%	$209.918	$209.92	$209.90	$209.90
Purchase #7	$76.53	12.842%	$86.358	$86.36	$86.35	$86.40
7 purchase totals =	$825.10		$900.8752	$900.87	$900.80	$901.00