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	$199.44	10.805%	$220.9895	$220.99	$221.00	$221.00
Purchase #2	$181.98	8.156%	$196.8223	$196.82	$196.80	$196.80
Purchase #3	$104.41	3.606%	$108.175	$108.18	$108.20	$108.20
Purchase #4	$178.91	6.424%	$190.4032	$190.40	$190.40	$190.40
Purchase #5	$54.69	11.141%	$60.783	$60.78	$60.80	$60.80
Purchase #6	$91.72	13.589%	$104.1838	$104.18	$104.20	$104.20
Purchase #7	$172.88	10.414%	$190.8837	$190.88	$190.90	$190.90
7 purchase totals =	$984.03		$1,072.2405	$1,072.23	$1,072.30	$1,072.30