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	$188.98	12.564%	$212.7234	$212.72	$212.70	$212.70
Purchase #2	$187.56	4.532%	$196.0602	$196.06	$196.05	$196.10
Purchase #3	$73.63	13.300%	$83.4228	$83.42	$83.40	$83.40
Purchase #4	$137.27	9.469%	$150.2681	$150.27	$150.25	$150.30
Purchase #5	$167.74	5.185%	$176.4373	$176.44	$176.45	$176.40
Purchase #6	$172.82	8.227%	$187.0379	$187.04	$187.05	$187.00
Purchase #7	$33.41	8.164%	$36.1376	$36.14	$36.15	$36.10
7 purchase totals =	$961.41		$1,042.0873	$1,042.09	$1,042.05	$1,042.00