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	$227.93	5.356%	$240.1379	$240.14	$240.15	$240.10
Purchase #2	$79.56	3.705%	$82.5077	$82.51	$82.50	$82.50
Purchase #3	$92.97	6.118%	$98.6579	$98.66	$98.65	$98.70
Purchase #4	$51.56	7.433%	$55.3925	$55.39	$55.40	$55.40
Purchase #5	$96.50	7.873%	$104.0974	$104.10	$104.10	$104.10
Purchase #6	$44.78	13.395%	$50.7783	$50.78	$50.80	$50.80
Purchase #7	$245.36	7.505%	$263.7743	$263.77	$263.75	$263.80
7 purchase totals =	$838.66		$895.3460	$895.35	$895.35	$895.40