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	$68.51	10.747%	$75.8728	$75.87	$75.85	$75.90
Purchase #2	$55.60	7.546%	$59.7956	$59.80	$59.80	$59.80
Purchase #3	$121.53	7.742%	$130.9389	$130.94	$130.95	$130.90
Purchase #4	$167.29	11.357%	$186.2891	$186.29	$186.30	$186.30
Purchase #5	$136.39	10.196%	$150.2963	$150.30	$150.30	$150.30
Purchase #6	$82.39	10.150%	$90.7526	$90.75	$90.75	$90.80
Purchase #7	$212.62	9.243%	$232.2725	$232.27	$232.25	$232.30
7 purchase totals =	$844.33		$926.2178	$926.22	$926.20	$926.30