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	$169.39	5.792%	$179.2011	$179.20	$179.20	$179.20
Purchase #2	$139.77	8.695%	$151.923	$151.92	$151.90	$151.90
Purchase #3	$118.92	10.493%	$131.3983	$131.40	$131.40	$131.40
Purchase #4	$136.92	6.227%	$145.446	$145.45	$145.45	$145.40
Purchase #5	$139.37	5.812%	$147.4702	$147.47	$147.45	$147.50
Purchase #6	$210.34	3.839%	$218.415	$218.42	$218.40	$218.40
Purchase #7	$97.36	11.709%	$108.7599	$108.76	$108.75	$108.80
7 purchase totals =	$1,012.07		$1,082.6135	$1,082.62	$1,082.55	$1,082.60