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	$96.92	6.608%	$103.3245	$103.32	$103.30	$103.30
Purchase #2	$232.92	9.858%	$255.8813	$255.88	$255.90	$255.90
Purchase #3	$204.43	4.199%	$213.014	$213.01	$213.00	$213.00
Purchase #4	$76.95	12.408%	$86.498	$86.50	$86.50	$86.50
Purchase #5	$65.26	9.356%	$71.3657	$71.37	$71.35	$71.40
Purchase #6	$113.78	8.542%	$123.4991	$123.50	$123.50	$123.50
Purchase #7	$174.36	8.109%	$188.4989	$188.50	$188.50	$188.50
7 purchase totals =	$964.62		$1,042.0815	$1,042.08	$1,042.05	$1,042.10