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	$71.44	3.494%	$73.9361	$73.94	$73.95	$73.90
Purchase #2	$114.39	8.251%	$123.8283	$123.83	$123.85	$123.80
Purchase #3	$81.52	10.597%	$90.1587	$90.16	$90.15	$90.20
Purchase #4	$81.95	3.774%	$85.0428	$85.04	$85.05	$85.00
Purchase #5	$156.73	6.407%	$166.7717	$166.77	$166.75	$166.80
Purchase #6	$210.32	6.385%	$223.7489	$223.75	$223.75	$223.70
Purchase #7	$122.96	7.666%	$132.3861	$132.39	$132.40	$132.40
7 purchase totals =	$839.31		$895.8726	$895.88	$895.90	$895.80