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	$165.98	12.217%	$186.2578	$186.26	$186.25	$186.30
Purchase #2	$204.70	4.337%	$213.5778	$213.58	$213.60	$213.60
Purchase #3	$28.32	3.651%	$29.354	$29.35	$29.35	$29.40
Purchase #4	$248.76	13.498%	$282.3376	$282.34	$282.35	$282.30
Purchase #5	$37.61	13.201%	$42.5749	$42.57	$42.55	$42.60
Purchase #6	$108.30	7.517%	$116.4409	$116.44	$116.45	$116.40
Purchase #7	$192.94	9.307%	$210.8969	$210.90	$210.90	$210.90
7 purchase totals =	$986.61		$1,081.4399	$1,081.44	$1,081.45	$1,081.50