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	$227.45	4.524%	$237.7398	$237.74	$237.75	$237.70
Purchase #2	$57.93	3.408%	$59.9043	$59.90	$59.90	$59.90
Purchase #3	$90.82	12.740%	$102.3905	$102.39	$102.40	$102.40
Purchase #4	$103.48	6.615%	$110.3252	$110.33	$110.35	$110.30
Purchase #5	$159.71	9.747%	$175.2769	$175.28	$175.30	$175.30
Purchase #6	$122.97	4.467%	$128.4631	$128.46	$128.45	$128.50
Purchase #7	$205.47	5.235%	$216.2264	$216.23	$216.25	$216.20
7 purchase totals =	$967.83		$1,030.3262	$1,030.33	$1,030.40	$1,030.30