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	$187.72	13.554%	$213.1636	$213.16	$213.15	$213.20
Purchase #2	$80.51	7.386%	$86.4565	$86.46	$86.45	$86.50
Purchase #3	$166.53	8.246%	$180.2621	$180.26	$180.25	$180.30
Purchase #4	$96.59	4.754%	$101.1819	$101.18	$101.20	$101.20
Purchase #5	$68.91	3.713%	$71.4686	$71.47	$71.45	$71.50
Purchase #6	$191.70	3.514%	$198.4363	$198.44	$198.45	$198.40
Purchase #7	$87.59	4.465%	$91.5009	$91.50	$91.50	$91.50
7 purchase totals =	$879.55		$942.4699	$942.47	$942.45	$942.60