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	$150.43	13.494%	$170.729	$170.73	$170.75	$170.70
Purchase #2	$48.33	3.785%	$50.1593	$50.16	$50.15	$50.20
Purchase #3	$101.49	9.528%	$111.16	$111.16	$111.15	$111.20
Purchase #4	$202.85	12.609%	$228.4274	$228.43	$228.45	$228.40
Purchase #5	$155.92	12.193%	$174.9313	$174.93	$174.95	$174.90
Purchase #6	$92.27	11.148%	$102.5563	$102.56	$102.55	$102.60
Purchase #7	$157.60	3.164%	$162.5865	$162.59	$162.60	$162.60
7 purchase totals =	$908.89		$1,000.5498	$1,000.56	$1,000.60	$1,000.60