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	$95.99	7.868%	$103.5425	$103.54	$103.55	$103.50
Purchase #2	$246.60	8.743%	$268.1602	$268.16	$268.15	$268.20
Purchase #3	$220.39	11.170%	$245.0076	$245.01	$245.00	$245.00
Purchase #4	$55.30	8.349%	$59.917	$59.92	$59.90	$59.90
Purchase #5	$227.59	10.149%	$250.6881	$250.69	$250.70	$250.70
Purchase #6	$53.42	3.696%	$55.3944	$55.39	$55.40	$55.40
Purchase #7	$31.34	4.679%	$32.8064	$32.81	$32.80	$32.80
7 purchase totals =	$930.63		$1,015.5162	$1,015.52	$1,015.50	$1,015.50