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	$195.90	3.740%	$203.2267	$203.23	$203.25	$203.20
Purchase #2	$130.48	6.384%	$138.8098	$138.81	$138.80	$138.80
Purchase #3	$96.48	5.308%	$101.6012	$101.60	$101.60	$101.60
Purchase #4	$233.46	8.203%	$252.6107	$252.61	$252.60	$252.60
Purchase #5	$142.48	9.179%	$155.5582	$155.56	$155.55	$155.60
Purchase #6	$56.25	11.858%	$62.9201	$62.92	$62.90	$62.90
Purchase #7	$179.99	9.112%	$196.3907	$196.39	$196.40	$196.40
7 purchase totals =	$1,035.04		$1,111.1174	$1,111.12	$1,111.10	$1,111.10