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	$144.88	6.581%	$154.4146	$154.41	$154.40	$154.40
Purchase #2	$212.42	12.333%	$238.6178	$238.62	$238.60	$238.60
Purchase #3	$245.58	6.810%	$262.304	$262.30	$262.30	$262.30
Purchase #4	$245.96	7.154%	$263.556	$263.56	$263.55	$263.60
Purchase #5	$6.84	4.447%	$7.1442	$7.14	$7.15	$7.10
Purchase #6	$28.41	4.257%	$29.6194	$29.62	$29.60	$29.60
Purchase #7	$77.51	6.442%	$82.5032	$82.50	$82.50	$82.50
7 purchase totals =	$961.60		$1,038.1592	$1,038.15	$1,038.10	$1,038.10