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	$168.81	7.415%	$181.3273	$181.33	$181.35	$181.30
Purchase #2	$59.45	5.601%	$62.7798	$62.78	$62.80	$62.80
Purchase #3	$151.31	13.760%	$172.1303	$172.13	$172.15	$172.10
Purchase #4	$6.80	4.159%	$7.0828	$7.08	$7.10	$7.10
Purchase #5	$68.83	3.746%	$71.4084	$71.41	$71.40	$71.40
Purchase #6	$72.54	8.651%	$78.8154	$78.82	$78.80	$78.80
Purchase #7	$172.91	13.303%	$195.9122	$195.91	$195.90	$195.90
7 purchase totals =	$700.65		$769.4562	$769.46	$769.50	$769.40