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	$129.96	9.617%	$142.4583	$142.46	$142.45	$142.50
Purchase #2	$244.88	9.459%	$268.0432	$268.04	$268.05	$268.00
Purchase #3	$162.78	3.344%	$168.2234	$168.22	$168.20	$168.20
Purchase #4	$157.72	5.227%	$165.964	$165.96	$165.95	$166.00
Purchase #5	$31.43	9.109%	$34.293	$34.29	$34.30	$34.30
Purchase #6	$217.91	5.819%	$230.5902	$230.59	$230.60	$230.60
Purchase #7	$77.46	9.792%	$85.0449	$85.04	$85.05	$85.00
7 purchase totals =	$1,022.14		$1,094.6170	$1,094.60	$1,094.60	$1,094.60