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	$63.33	9.261%	$69.195	$69.20	$69.20	$69.20
Purchase #2	$164.77	10.596%	$182.229	$182.23	$182.25	$182.20
Purchase #3	$62.31	8.426%	$67.5602	$67.56	$67.55	$67.60
Purchase #4	$240.81	9.475%	$263.6267	$263.63	$263.65	$263.60
Purchase #5	$160.43	3.232%	$165.6151	$165.62	$165.60	$165.60
Purchase #6	$152.77	10.310%	$168.5206	$168.52	$168.50	$168.50
Purchase #7	$178.87	4.596%	$187.0909	$187.09	$187.10	$187.10
7 purchase totals =	$1,023.29		$1,103.8375	$1,103.85	$1,103.85	$1,103.80