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	$122.40	7.174%	$131.181	$131.18	$131.20	$131.20
Purchase #2	$73.32	6.519%	$78.0997	$78.10	$78.10	$78.10
Purchase #3	$154.91	12.510%	$174.2892	$174.29	$174.30	$174.30
Purchase #4	$168.54	3.829%	$174.9934	$174.99	$175.00	$175.00
Purchase #5	$192.95	12.232%	$216.5516	$216.55	$216.55	$216.60
Purchase #6	$32.29	4.783%	$33.8344	$33.83	$33.85	$33.80
Purchase #7	$59.33	5.317%	$62.4846	$62.48	$62.50	$62.50
7 purchase totals =	$803.74		$871.4339	$871.42	$871.50	$871.50