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	$121.48	7.813%	$130.9712	$130.97	$130.95	$131.00
Purchase #2	$248.34	7.117%	$266.0144	$266.01	$266.00	$266.00
Purchase #3	$82.68	3.253%	$85.3696	$85.37	$85.35	$85.40
Purchase #4	$58.83	6.134%	$62.4386	$62.44	$62.45	$62.40
Purchase #5	$86.62	13.562%	$98.3674	$98.37	$98.35	$98.40
Purchase #6	$117.89	4.478%	$123.1691	$123.17	$123.15	$123.20
Purchase #7	$232.91	8.868%	$253.5645	$253.56	$253.55	$253.60
7 purchase totals =	$948.75		$1,019.8948	$1,019.89	$1,019.80	$1,020.00