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	$171.56	9.859%	$188.4741	$188.47	$188.45	$188.50
Purchase #2	$53.27	11.460%	$59.3747	$59.37	$59.35	$59.40
Purchase #3	$208.30	3.464%	$215.5155	$215.52	$215.50	$215.50
Purchase #4	$113.97	7.396%	$122.3992	$122.40	$122.40	$122.40
Purchase #5	$53.60	4.699%	$56.1187	$56.12	$56.10	$56.10
Purchase #6	$114.97	9.433%	$125.8151	$125.82	$125.80	$125.80
Purchase #7	$223.77	11.401%	$249.282	$249.28	$249.30	$249.30
7 purchase totals =	$939.44		$1,016.9793	$1,016.98	$1,016.90	$1,017.00