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	$147.98	3.234%	$152.7657	$152.77	$152.75	$152.80
Purchase #2	$167.97	10.578%	$185.7379	$185.74	$185.75	$185.70
Purchase #3	$103.84	12.568%	$116.8906	$116.89	$116.90	$116.90
Purchase #4	$142.89	12.356%	$160.5455	$160.55	$160.55	$160.50
Purchase #5	$74.69	8.823%	$81.2799	$81.28	$81.30	$81.30
Purchase #6	$157.30	10.624%	$174.0116	$174.01	$174.00	$174.00
Purchase #7	$176.57	4.453%	$184.4327	$184.43	$184.45	$184.40
7 purchase totals =	$971.24		$1,055.6639	$1,055.67	$1,055.70	$1,055.60