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	$81.88	4.229%	$85.3427	$85.34	$85.35	$85.30
Purchase #2	$166.47	4.213%	$173.4834	$173.48	$173.50	$173.50
Purchase #3	$97.69	13.868%	$111.2376	$111.24	$111.25	$111.20
Purchase #4	$219.63	5.836%	$232.4476	$232.45	$232.45	$232.40
Purchase #5	$53.86	13.645%	$61.2092	$61.21	$61.20	$61.20
Purchase #6	$57.70	13.207%	$65.3204	$65.32	$65.30	$65.30
Purchase #7	$204.38	4.471%	$213.5178	$213.52	$213.50	$213.50
7 purchase totals =	$881.61		$942.5587	$942.56	$942.55	$942.40