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	$186.98	10.591%	$206.7831	$206.78	$206.80	$206.80
Purchase #2	$103.71	11.308%	$115.4375	$115.44	$115.45	$115.40
Purchase #3	$7.61	8.780%	$8.2782	$8.28	$8.30	$8.30
Purchase #4	$167.59	12.379%	$188.336	$188.34	$188.35	$188.30
Purchase #5	$196.78	3.468%	$203.6043	$203.60	$203.60	$203.60
Purchase #6	$86.53	3.343%	$89.4227	$89.42	$89.40	$89.40
Purchase #7	$180.85	13.519%	$205.2991	$205.30	$205.30	$205.30
7 purchase totals =	$930.05		$1,017.1609	$1,017.16	$1,017.20	$1,017.10