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	$75.34	8.496%	$81.7409	$81.74	$81.75	$81.70
Purchase #2	$159.78	8.127%	$172.7653	$172.77	$172.75	$172.80
Purchase #3	$131.78	7.107%	$141.1456	$141.15	$141.15	$141.10
Purchase #4	$243.83	9.510%	$267.0182	$267.02	$267.00	$267.00
Purchase #5	$52.76	12.467%	$59.3376	$59.34	$59.35	$59.30
Purchase #6	$159.47	9.153%	$174.0663	$174.07	$174.05	$174.10
Purchase #7	$142.68	6.489%	$151.9385	$151.94	$151.95	$151.90
7 purchase totals =	$965.64		$1,048.0124	$1,048.03	$1,048.00	$1,047.90