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	$103.37	6.748%	$110.3454	$110.35	$110.35	$110.30
Purchase #2	$213.46	9.556%	$233.8582	$233.86	$233.85	$233.90
Purchase #3	$210.33	11.212%	$233.9122	$233.91	$233.90	$233.90
Purchase #4	$179.65	4.710%	$188.1115	$188.11	$188.10	$188.10
Purchase #5	$182.33	11.509%	$203.3144	$203.31	$203.30	$203.30
Purchase #6	$102.39	6.479%	$109.0238	$109.02	$109.00	$109.00
Purchase #7	$45.51	11.820%	$50.8893	$50.89	$50.90	$50.90
7 purchase totals =	$1,037.04		$1,129.4548	$1,129.45	$1,129.40	$1,129.40