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	$98.27	8.780%	$106.8981	$106.90	$106.90	$106.90
Purchase #2	$107.99	13.226%	$122.2728	$122.27	$122.25	$122.30
Purchase #3	$31.62	5.418%	$33.3332	$33.33	$33.35	$33.30
Purchase #4	$116.98	5.403%	$123.3004	$123.30	$123.30	$123.30
Purchase #5	$79.90	4.793%	$83.7296	$83.73	$83.75	$83.70
Purchase #6	$55.78	10.180%	$61.4584	$61.46	$61.45	$61.50
Purchase #7	$213.98	6.260%	$227.3751	$227.38	$227.40	$227.40
7 purchase totals =	$704.52		$758.3676	$758.37	$758.40	$758.40