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	$162.64	3.762%	$168.7585	$168.76	$168.75	$168.80
Purchase #2	$98.59	7.254%	$105.7417	$105.74	$105.75	$105.70
Purchase #3	$136.86	6.793%	$146.1569	$146.16	$146.15	$146.20
Purchase #4	$158.48	6.336%	$168.5213	$168.52	$168.50	$168.50
Purchase #5	$142.58	12.835%	$160.8801	$160.88	$160.90	$160.90
Purchase #6	$244.69	8.819%	$266.2692	$266.27	$266.25	$266.30
Purchase #7	$199.50	13.754%	$226.9392	$226.94	$226.95	$226.90
7 purchase totals =	$1,143.34		$1,243.2669	$1,243.27	$1,243.25	$1,243.30