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	$85.78	7.343%	$92.0788	$92.08	$92.10	$92.10
Purchase #2	$112.55	3.211%	$116.164	$116.16	$116.15	$116.20
Purchase #3	$116.49	6.306%	$123.8359	$123.84	$123.85	$123.80
Purchase #4	$148.44	5.204%	$156.1648	$156.16	$156.15	$156.20
Purchase #5	$25.54	13.191%	$28.909	$28.91	$28.90	$28.90
Purchase #6	$211.60	11.152%	$235.1976	$235.20	$235.20	$235.20
Purchase #7	$188.44	4.211%	$196.3752	$196.38	$196.40	$196.40
7 purchase totals =	$888.84		$948.7253	$948.73	$948.75	$948.80