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	$88.72	3.192%	$91.5519	$91.55	$91.55	$91.60
Purchase #2	$44.35	10.770%	$49.1265	$49.13	$49.15	$49.10
Purchase #3	$41.97	13.145%	$47.487	$47.49	$47.50	$47.50
Purchase #4	$89.76	10.784%	$99.4397	$99.44	$99.45	$99.40
Purchase #5	$106.52	10.440%	$117.6407	$117.64	$117.65	$117.60
Purchase #6	$46.66	10.234%	$51.4352	$51.44	$51.45	$51.40
Purchase #7	$79.84	8.240%	$86.4188	$86.42	$86.40	$86.40
7 purchase totals =	$497.82		$543.0998	$543.11	$543.15	$543.00