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	$98.72	11.697%	$110.2673	$110.27	$110.25	$110.30
Purchase #2	$219.65	12.817%	$247.8025	$247.80	$247.80	$247.80
Purchase #3	$209.56	6.271%	$222.7015	$222.70	$222.70	$222.70
Purchase #4	$161.28	3.431%	$166.8135	$166.81	$166.80	$166.80
Purchase #5	$180.92	8.613%	$196.5026	$196.50	$196.50	$196.50
Purchase #6	$88.40	13.749%	$100.5541	$100.55	$100.55	$100.60
Purchase #7	$206.96	9.331%	$226.2714	$226.27	$226.25	$226.30
7 purchase totals =	$1,165.49		$1,270.9129	$1,270.90	$1,270.85	$1,271.00