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	$134.66	13.358%	$152.6479	$152.65	$152.65	$152.60
Purchase #2	$101.63	6.187%	$107.9178	$107.92	$107.90	$107.90
Purchase #3	$217.78	4.838%	$228.3162	$228.32	$228.30	$228.30
Purchase #4	$96.51	12.514%	$108.5873	$108.59	$108.60	$108.60
Purchase #5	$167.83	10.755%	$185.8801	$185.88	$185.90	$185.90
Purchase #6	$212.61	4.755%	$222.7196	$222.72	$222.70	$222.70
Purchase #7	$165.74	8.133%	$179.2196	$179.22	$179.20	$179.20
7 purchase totals =	$1,096.76		$1,185.2885	$1,185.30	$1,185.25	$1,185.20