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	$90.44	6.254%	$96.0961	$96.10	$96.10	$96.10
Purchase #2	$60.81	7.398%	$65.3087	$65.31	$65.30	$65.30
Purchase #3	$96.34	7.818%	$103.8719	$103.87	$103.85	$103.90
Purchase #4	$183.90	6.716%	$196.2507	$196.25	$196.25	$196.30
Purchase #5	$9.27	12.122%	$10.3937	$10.39	$10.40	$10.40
Purchase #6	$218.61	10.420%	$241.3892	$241.39	$241.40	$241.40
Purchase #7	$194.68	10.257%	$214.6483	$214.65	$214.65	$214.60
7 purchase totals =	$854.05		$927.9586	$927.96	$927.95	$928.00