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	$10.49	10.272%	$11.5675	$11.57	$11.55	$11.60
Purchase #2	$28.85	8.370%	$31.2647	$31.26	$31.25	$31.30
Purchase #3	$90.51	5.396%	$95.3939	$95.39	$95.40	$95.40
Purchase #4	$84.45	13.563%	$95.904	$95.90	$95.90	$95.90
Purchase #5	$28.29	9.216%	$30.8972	$30.90	$30.90	$30.90
Purchase #6	$50.52	11.402%	$56.2803	$56.28	$56.30	$56.30
Purchase #7	$223.50	11.663%	$249.5668	$249.57	$249.55	$249.60
7 purchase totals =	$516.61		$570.8744	$570.87	$570.85	$571.00