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	$157.79	10.552%	$174.44	$174.44	$174.45	$174.40
Purchase #2	$241.86	10.356%	$266.907	$266.91	$266.90	$266.90
Purchase #3	$28.51	9.178%	$31.1266	$31.13	$31.15	$31.10
Purchase #4	$163.35	11.600%	$182.2986	$182.30	$182.30	$182.30
Purchase #5	$62.63	4.113%	$65.206	$65.21	$65.20	$65.20
Purchase #6	$33.43	11.218%	$37.1802	$37.18	$37.20	$37.20
Purchase #7	$48.33	4.248%	$50.3831	$50.38	$50.40	$50.40
7 purchase totals =	$735.90		$807.5415	$807.55	$807.60	$807.50