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	$183.70	13.107%	$207.7776	$207.78	$207.80	$207.80
Purchase #2	$248.72	5.163%	$261.5614	$261.56	$261.55	$261.60
Purchase #3	$202.57	3.818%	$210.3041	$210.30	$210.30	$210.30
Purchase #4	$93.55	11.481%	$104.2905	$104.29	$104.30	$104.30
Purchase #5	$145.44	13.192%	$164.6264	$164.63	$164.65	$164.60
Purchase #6	$52.41	12.724%	$59.0786	$59.08	$59.10	$59.10
Purchase #7	$78.59	8.753%	$85.469	$85.47	$85.45	$85.50
7 purchase totals =	$1,004.98		$1,093.1076	$1,093.11	$1,093.15	$1,093.20