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	$184.32	13.572%	$209.3359	$209.34	$209.35	$209.30
Purchase #2	$42.80	5.631%	$45.2101	$45.21	$45.20	$45.20
Purchase #3	$165.98	3.381%	$171.5918	$171.59	$171.60	$171.60
Purchase #4	$241.91	3.290%	$249.8688	$249.87	$249.85	$249.90
Purchase #5	$6.83	8.565%	$7.415	$7.42	$7.40	$7.40
Purchase #6	$154.88	7.592%	$166.6385	$166.64	$166.65	$166.60
Purchase #7	$209.57	9.314%	$229.0893	$229.09	$229.10	$229.10
7 purchase totals =	$1,006.29		$1,079.1494	$1,079.16	$1,079.15	$1,079.10