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	$183.90	13.772%	$209.2267	$209.23	$209.25	$209.20
Purchase #2	$171.96	12.677%	$193.7594	$193.76	$193.75	$193.80
Purchase #3	$228.38	5.212%	$240.2832	$240.28	$240.30	$240.30
Purchase #4	$24.93	10.658%	$27.587	$27.59	$27.60	$27.60
Purchase #5	$72.88	5.107%	$76.602	$76.60	$76.60	$76.60
Purchase #6	$232.73	6.384%	$247.5875	$247.59	$247.60	$247.60
Purchase #7	$68.94	3.800%	$71.5597	$71.56	$71.55	$71.60
7 purchase totals =	$983.72		$1,066.6055	$1,066.61	$1,066.65	$1,066.70