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	$238.81	11.786%	$266.9561	$266.96	$266.95	$267.00
Purchase #2	$220.34	6.487%	$234.6335	$234.63	$234.65	$234.60
Purchase #3	$179.70	3.132%	$185.3282	$185.33	$185.35	$185.30
Purchase #4	$148.95	7.742%	$160.4817	$160.48	$160.50	$160.50
Purchase #5	$64.26	5.693%	$67.9183	$67.92	$67.90	$67.90
Purchase #6	$57.86	4.215%	$60.2988	$60.30	$60.30	$60.30
Purchase #7	$152.86	12.614%	$172.1418	$172.14	$172.15	$172.10
7 purchase totals =	$1,062.78		$1,147.7584	$1,147.76	$1,147.80	$1,147.70