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	$185.98	10.454%	$205.4223	$205.42	$205.40	$205.40
Purchase #2	$209.93	3.756%	$217.815	$217.82	$217.80	$217.80
Purchase #3	$79.32	13.424%	$89.9679	$89.97	$89.95	$90.00
Purchase #4	$91.34	8.739%	$99.3222	$99.32	$99.30	$99.30
Purchase #5	$131.49	7.484%	$141.3307	$141.33	$141.35	$141.30
Purchase #6	$144.51	8.429%	$156.6907	$156.69	$156.70	$156.70
Purchase #7	$98.40	5.322%	$103.6368	$103.64	$103.65	$103.60
7 purchase totals =	$940.97		$1,014.1856	$1,014.19	$1,014.15	$1,014.10