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	$228.55	4.202%	$238.1537	$238.15	$238.15	$238.20
Purchase #2	$48.29	11.788%	$53.9824	$53.98	$54.00	$54.00
Purchase #3	$148.40	9.779%	$162.912	$162.91	$162.90	$162.90
Purchase #4	$203.72	7.667%	$219.3392	$219.34	$219.35	$219.30
Purchase #5	$56.72	4.621%	$59.341	$59.34	$59.35	$59.30
Purchase #6	$85.51	12.545%	$96.2372	$96.24	$96.25	$96.20
Purchase #7	$49.60	7.563%	$53.3512	$53.35	$53.35	$53.40
7 purchase totals =	$820.79		$883.3167	$883.31	$883.35	$883.30