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	$158.90	9.764%	$174.415	$174.42	$174.40	$174.40
Purchase #2	$94.32	8.392%	$102.2353	$102.24	$102.25	$102.20
Purchase #3	$35.99	12.733%	$40.5726	$40.57	$40.55	$40.60
Purchase #4	$131.94	10.646%	$145.9863	$145.99	$146.00	$146.00
Purchase #5	$63.86	11.408%	$71.1451	$71.15	$71.15	$71.10
Purchase #6	$200.71	7.190%	$215.141	$215.14	$215.15	$215.10
Purchase #7	$96.29	7.822%	$103.8218	$103.82	$103.80	$103.80
7 purchase totals =	$782.01		$853.3171	$853.33	$853.30	$853.20