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	$142.80	12.582%	$160.7671	$160.77	$160.75	$160.80
Purchase #2	$135.62	5.728%	$143.3883	$143.39	$143.40	$143.40
Purchase #3	$41.84	7.547%	$44.9977	$45.00	$45.00	$45.00
Purchase #4	$72.92	7.817%	$78.6202	$78.62	$78.60	$78.60
Purchase #5	$182.88	7.502%	$196.5997	$196.60	$196.60	$196.60
Purchase #6	$118.82	9.409%	$129.9998	$130.00	$130.00	$130.00
Purchase #7	$111.33	11.600%	$124.2443	$124.24	$124.25	$124.20
7 purchase totals =	$806.21		$878.6171	$878.62	$878.60	$878.60