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	$231.94	6.628%	$247.313	$247.31	$247.30	$247.30
Purchase #2	$162.92	3.616%	$168.8112	$168.81	$168.80	$168.80
Purchase #3	$159.97	6.725%	$170.728	$170.73	$170.75	$170.70
Purchase #4	$111.25	11.111%	$123.611	$123.61	$123.60	$123.60
Purchase #5	$16.54	6.488%	$17.6131	$17.61	$17.60	$17.60
Purchase #6	$96.27	13.579%	$109.3425	$109.34	$109.35	$109.30
Purchase #7	$169.78	12.625%	$191.2147	$191.21	$191.20	$191.20
7 purchase totals =	$948.67		$1,028.6335	$1,028.62	$1,028.60	$1,028.50