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	$22.95	5.744%	$24.2682	$24.27	$24.25	$24.30
Purchase #2	$85.93	4.369%	$89.6843	$89.68	$89.70	$89.70
Purchase #3	$170.89	11.253%	$190.1203	$190.12	$190.10	$190.10
Purchase #4	$239.77	6.154%	$254.5254	$254.53	$254.55	$254.50
Purchase #5	$100.98	4.838%	$105.8654	$105.87	$105.85	$105.90
Purchase #6	$154.85	9.699%	$169.8689	$169.87	$169.85	$169.90
Purchase #7	$156.44	11.471%	$174.3852	$174.39	$174.40	$174.40
7 purchase totals =	$931.81		$1,008.7177	$1,008.73	$1,008.70	$1,008.80