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	$131.66	7.154%	$141.079	$141.08	$141.10	$141.10
Purchase #2	$37.78	11.827%	$42.2482	$42.25	$42.25	$42.20
Purchase #3	$61.33	3.154%	$63.2643	$63.26	$63.25	$63.30
Purchase #4	$218.32	12.467%	$245.538	$245.54	$245.55	$245.50
Purchase #5	$51.84	6.372%	$55.1432	$55.14	$55.15	$55.10
Purchase #6	$185.72	7.810%	$200.2247	$200.22	$200.20	$200.20
Purchase #7	$138.79	4.645%	$145.2368	$145.24	$145.25	$145.20
7 purchase totals =	$825.44		$892.7342	$892.73	$892.75	$892.60