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	$220.56	8.247%	$238.7496	$238.75	$238.75	$238.70
Purchase #2	$166.35	12.755%	$187.5679	$187.57	$187.55	$187.60
Purchase #3	$91.85	12.774%	$103.5829	$103.58	$103.60	$103.60
Purchase #4	$45.33	7.834%	$48.8812	$48.88	$48.90	$48.90
Purchase #5	$241.70	5.603%	$255.2425	$255.24	$255.25	$255.20
Purchase #6	$162.92	3.195%	$168.1253	$168.13	$168.15	$168.10
Purchase #7	$44.63	9.281%	$48.7721	$48.77	$48.75	$48.80
7 purchase totals =	$973.34		$1,050.9215	$1,050.92	$1,050.95	$1,050.90