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	$162.59	13.611%	$184.7201	$184.72	$184.70	$184.70
Purchase #2	$118.91	5.350%	$125.2717	$125.27	$125.25	$125.30
Purchase #3	$38.42	4.867%	$40.2899	$40.29	$40.30	$40.30
Purchase #4	$31.44	10.185%	$34.6422	$34.64	$34.65	$34.60
Purchase #5	$215.62	9.839%	$236.8349	$236.83	$236.85	$236.80
Purchase #6	$82.73	8.351%	$89.6388	$89.64	$89.65	$89.60
Purchase #7	$187.80	11.776%	$209.9153	$209.92	$209.90	$209.90
7 purchase totals =	$837.51		$921.3129	$921.31	$921.30	$921.20