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	$54.85	8.182%	$59.3378	$59.34	$59.35	$59.30
Purchase #2	$47.87	6.801%	$51.1256	$51.13	$51.15	$51.10
Purchase #3	$246.80	9.361%	$269.9029	$269.90	$269.90	$269.90
Purchase #4	$12.38	3.502%	$12.8135	$12.81	$12.80	$12.80
Purchase #5	$99.57	10.319%	$109.8446	$109.84	$109.85	$109.80
Purchase #6	$128.86	6.276%	$136.9473	$136.95	$136.95	$136.90
Purchase #7	$69.40	5.587%	$73.2774	$73.28	$73.30	$73.30
7 purchase totals =	$659.73		$713.2491	$713.25	$713.30	$713.10