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	$235.66	5.266%	$248.0699	$248.07	$248.05	$248.10
Purchase #2	$100.87	10.462%	$111.423	$111.42	$111.40	$111.40
Purchase #3	$176.63	10.740%	$195.6001	$195.60	$195.60	$195.60
Purchase #4	$205.40	11.555%	$229.134	$229.13	$229.15	$229.10
Purchase #5	$123.63	10.676%	$136.8287	$136.83	$136.85	$136.80
Purchase #6	$117.69	5.559%	$124.2324	$124.23	$124.25	$124.20
Purchase #7	$90.84	12.136%	$101.8643	$101.86	$101.85	$101.90
7 purchase totals =	$1,050.72		$1,147.1524	$1,147.14	$1,147.15	$1,147.10