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	$187.89	8.712%	$204.259	$204.26	$204.25	$204.30
Purchase #2	$126.70	8.688%	$137.7077	$137.71	$137.70	$137.70
Purchase #3	$168.28	11.806%	$188.1471	$188.15	$188.15	$188.10
Purchase #4	$131.63	11.534%	$146.8122	$146.81	$146.80	$146.80
Purchase #5	$61.60	5.705%	$65.1143	$65.11	$65.10	$65.10
Purchase #6	$145.29	7.686%	$156.457	$156.46	$156.45	$156.50
Purchase #7	$204.78	8.808%	$222.817	$222.82	$222.80	$222.80
7 purchase totals =	$1,026.17		$1,121.3143	$1,121.32	$1,121.25	$1,121.30