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	$5.57	5.251%	$5.8625	$5.86	$5.85	$5.90
Purchase #2	$52.84	8.269%	$57.2093	$57.21	$57.20	$57.20
Purchase #3	$41.34	9.229%	$45.1553	$45.16	$45.15	$45.20
Purchase #4	$106.30	6.427%	$113.1319	$113.13	$113.15	$113.10
Purchase #5	$82.77	11.252%	$92.0833	$92.08	$92.10	$92.10
Purchase #6	$54.65	5.321%	$57.5579	$57.56	$57.55	$57.60
Purchase #7	$82.51	3.509%	$85.4053	$85.41	$85.40	$85.40
7 purchase totals =	$425.98		$456.4055	$456.41	$456.40	$456.50