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	$207.69	9.527%	$227.4766	$227.48	$227.50	$227.50
Purchase #2	$127.45	4.442%	$133.1113	$133.11	$133.10	$133.10
Purchase #3	$25.42	13.745%	$28.914	$28.91	$28.90	$28.90
Purchase #4	$190.34	4.573%	$199.0442	$199.04	$199.05	$199.00
Purchase #5	$54.77	9.497%	$59.9715	$59.97	$59.95	$60.00
Purchase #6	$19.80	11.685%	$22.1136	$22.11	$22.10	$22.10
Purchase #7	$96.46	13.591%	$109.5699	$109.57	$109.55	$109.60
7 purchase totals =	$721.93		$780.2011	$780.19	$780.15	$780.20