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	$198.32	5.553%	$209.3327	$209.33	$209.35	$209.30
Purchase #2	$180.75	5.606%	$190.8828	$190.88	$190.90	$190.90
Purchase #3	$53.59	3.240%	$55.3263	$55.33	$55.35	$55.30
Purchase #4	$80.70	11.491%	$89.9732	$89.97	$89.95	$90.00
Purchase #5	$71.78	4.232%	$74.8177	$74.82	$74.80	$74.80
Purchase #6	$127.40	9.646%	$139.689	$139.69	$139.70	$139.70
Purchase #7	$226.64	9.346%	$247.8218	$247.82	$247.80	$247.80
7 purchase totals =	$939.18		$1,007.8435	$1,007.84	$1,007.85	$1,007.80