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	$165.96	6.825%	$177.2868	$177.29	$177.30	$177.30
Purchase #2	$79.37	4.307%	$82.7885	$82.79	$82.80	$82.80
Purchase #3	$143.89	6.421%	$153.1292	$153.13	$153.15	$153.10
Purchase #4	$136.46	11.610%	$152.303	$152.30	$152.30	$152.30
Purchase #5	$147.47	8.539%	$160.0625	$160.06	$160.05	$160.10
Purchase #6	$97.34	6.825%	$103.9835	$103.98	$104.00	$104.00
Purchase #7	$172.67	8.522%	$187.3849	$187.38	$187.40	$187.40
7 purchase totals =	$943.16		$1,016.9384	$1,016.93	$1,017.00	$1,017.00