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	$141.99	6.373%	$151.039	$151.04	$151.05	$151.00
Purchase #2	$172.56	5.632%	$182.2786	$182.28	$182.30	$182.30
Purchase #3	$28.91	9.554%	$31.6721	$31.67	$31.65	$31.70
Purchase #4	$93.28	6.709%	$99.5382	$99.54	$99.55	$99.50
Purchase #5	$11.73	8.622%	$12.7414	$12.74	$12.75	$12.70
Purchase #6	$134.59	7.578%	$144.7892	$144.79	$144.80	$144.80
Purchase #7	$41.83	12.253%	$46.9554	$46.96	$46.95	$47.00
7 purchase totals =	$624.89		$669.0139	$669.02	$669.05	$669.00