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	$145.99	7.698%	$157.2283	$157.23	$157.25	$157.20
Purchase #2	$174.28	12.615%	$196.2654	$196.27	$196.25	$196.30
Purchase #3	$180.61	4.873%	$189.4111	$189.41	$189.40	$189.40
Purchase #4	$66.54	7.416%	$71.4746	$71.47	$71.45	$71.50
Purchase #5	$69.62	10.417%	$76.8723	$76.87	$76.85	$76.90
Purchase #6	$102.54	9.200%	$111.9737	$111.97	$111.95	$112.00
Purchase #7	$86.91	4.547%	$90.8618	$90.86	$90.85	$90.90
7 purchase totals =	$826.49		$894.0872	$894.08	$894.00	$894.20