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	$134.81	11.701%	$150.5841	$150.58	$150.60	$150.60
Purchase #2	$235.39	8.517%	$255.4382	$255.44	$255.45	$255.40
Purchase #3	$39.55	3.672%	$41.0023	$41.00	$41.00	$41.00
Purchase #4	$176.76	4.556%	$184.8132	$184.81	$184.80	$184.80
Purchase #5	$180.36	8.264%	$195.265	$195.27	$195.25	$195.30
Purchase #6	$69.65	3.463%	$72.062	$72.06	$72.05	$72.10
Purchase #7	$154.27	5.112%	$162.1563	$162.16	$162.15	$162.20
7 purchase totals =	$990.79		$1,061.3211	$1,061.32	$1,061.30	$1,061.40