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	$176.59	5.843%	$186.9082	$186.91	$186.90	$186.90
Purchase #2	$141.34	6.437%	$150.4381	$150.44	$150.45	$150.40
Purchase #3	$159.27	8.171%	$172.284	$172.28	$172.30	$172.30
Purchase #4	$17.34	13.804%	$19.7336	$19.73	$19.75	$19.70
Purchase #5	$167.50	10.170%	$184.5348	$184.53	$184.55	$184.50
Purchase #6	$130.59	4.330%	$136.2445	$136.24	$136.25	$136.20
Purchase #7	$198.55	6.479%	$211.4141	$211.41	$211.40	$211.40
7 purchase totals =	$991.18		$1,061.5573	$1,061.54	$1,061.60	$1,061.40