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	$86.58	11.695%	$96.7055	$96.71	$96.70	$96.70
Purchase #2	$242.37	12.600%	$272.9086	$272.91	$272.90	$272.90
Purchase #3	$151.90	12.720%	$171.2217	$171.22	$171.20	$171.20
Purchase #4	$54.38	5.804%	$57.5362	$57.54	$57.55	$57.50
Purchase #5	$152.39	13.346%	$172.728	$172.73	$172.75	$172.70
Purchase #6	$53.40	12.397%	$60.02	$60.02	$60.00	$60.00
Purchase #7	$242.27	9.736%	$265.8574	$265.86	$265.85	$265.90
7 purchase totals =	$983.29		$1,096.9774	$1,096.99	$1,096.95	$1,096.90