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	$82.61	8.559%	$89.6806	$89.68	$89.70	$89.70
Purchase #2	$69.82	13.560%	$79.2876	$79.29	$79.30	$79.30
Purchase #3	$205.40	9.835%	$225.6011	$225.60	$225.60	$225.60
Purchase #4	$134.69	11.441%	$150.0999	$150.10	$150.10	$150.10
Purchase #5	$194.93	12.306%	$218.9181	$218.92	$218.90	$218.90
Purchase #6	$176.25	11.311%	$196.1856	$196.19	$196.20	$196.20
Purchase #7	$58.62	5.805%	$62.0229	$62.02	$62.00	$62.00
7 purchase totals =	$922.32		$1,021.7958	$1,021.80	$1,021.80	$1,021.80