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	$175.73	11.589%	$196.0953	$196.10	$196.10	$196.10
Purchase #2	$162.54	9.728%	$178.3519	$178.35	$178.35	$178.40
Purchase #3	$129.28	13.196%	$146.3398	$146.34	$146.35	$146.30
Purchase #4	$102.43	6.817%	$109.4127	$109.41	$109.40	$109.40
Purchase #5	$110.77	13.789%	$126.0441	$126.04	$126.05	$126.00
Purchase #6	$61.98	13.458%	$70.3213	$70.32	$70.30	$70.30
Purchase #7	$192.30	10.735%	$212.9434	$212.94	$212.95	$212.90
7 purchase totals =	$935.03		$1,039.5085	$1,039.50	$1,039.50	$1,039.40