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	$8.32	3.156%	$8.5826	$8.58	$8.60	$8.60
Purchase #2	$17.97	3.592%	$18.6155	$18.62	$18.60	$18.60
Purchase #3	$78.56	4.856%	$82.3749	$82.37	$82.35	$82.40
Purchase #4	$152.76	9.563%	$167.3684	$167.37	$167.35	$167.40
Purchase #5	$89.91	12.380%	$101.0409	$101.04	$101.05	$101.00
Purchase #6	$192.88	12.211%	$216.4326	$216.43	$216.45	$216.40
Purchase #7	$135.60	3.143%	$139.8619	$139.86	$139.85	$139.90
7 purchase totals =	$676.00		$734.2768	$734.27	$734.25	$734.30