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	$127.71	11.472%	$142.3609	$142.36	$142.35	$142.40
Purchase #2	$90.31	9.733%	$99.0999	$99.10	$99.10	$99.10
Purchase #3	$72.28	4.609%	$75.6114	$75.61	$75.60	$75.60
Purchase #4	$95.49	8.345%	$103.4586	$103.46	$103.45	$103.50
Purchase #5	$236.59	5.413%	$249.3966	$249.40	$249.40	$249.40
Purchase #6	$154.37	13.617%	$175.3906	$175.39	$175.40	$175.40
Purchase #7	$247.52	8.306%	$268.079	$268.08	$268.10	$268.10
7 purchase totals =	$1,024.27		$1,113.3970	$1,113.40	$1,113.40	$1,113.50