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	$181.56	5.769%	$192.0342	$192.03	$192.05	$192.00
Purchase #2	$64.58	10.582%	$71.4139	$71.41	$71.40	$71.40
Purchase #3	$74.95	3.178%	$77.3319	$77.33	$77.35	$77.30
Purchase #4	$205.96	4.536%	$215.3023	$215.30	$215.30	$215.30
Purchase #5	$243.89	10.401%	$269.257	$269.26	$269.25	$269.30
Purchase #6	$106.47	5.168%	$111.9724	$111.97	$111.95	$112.00
Purchase #7	$124.59	7.815%	$134.3267	$134.33	$134.35	$134.30
7 purchase totals =	$1,002.00		$1,071.6384	$1,071.63	$1,071.65	$1,071.60