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	$95.71	11.842%	$107.044	$107.04	$107.05	$107.00
Purchase #2	$154.57	5.192%	$162.5953	$162.60	$162.60	$162.60
Purchase #3	$81.38	9.492%	$89.1046	$89.10	$89.10	$89.10
Purchase #4	$35.88	8.689%	$38.9976	$39.00	$39.00	$39.00
Purchase #5	$173.95	3.468%	$179.9826	$179.98	$180.00	$180.00
Purchase #6	$168.47	11.767%	$188.2939	$188.29	$188.30	$188.30
Purchase #7	$70.51	11.666%	$78.7357	$78.74	$78.75	$78.70
7 purchase totals =	$780.47		$844.7537	$844.75	$844.80	$844.70