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	$42.98	11.804%	$48.0534	$48.05	$48.05	$48.10
Purchase #2	$184.81	12.531%	$207.9685	$207.97	$207.95	$208.00
Purchase #3	$110.40	5.277%	$116.2258	$116.23	$116.25	$116.20
Purchase #4	$78.27	5.243%	$82.3737	$82.37	$82.35	$82.40
Purchase #5	$52.98	6.343%	$56.3405	$56.34	$56.35	$56.30
Purchase #6	$53.56	10.441%	$59.1522	$59.15	$59.15	$59.20
Purchase #7	$50.33	4.446%	$52.5677	$52.57	$52.55	$52.60
7 purchase totals =	$573.33		$622.6818	$622.68	$622.65	$622.80