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	$147.92	5.671%	$156.3085	$156.31	$156.30	$156.30
Purchase #2	$173.45	3.766%	$179.9821	$179.98	$180.00	$180.00
Purchase #3	$236.46	4.636%	$247.4223	$247.42	$247.40	$247.40
Purchase #4	$69.50	3.501%	$71.9332	$71.93	$71.95	$71.90
Purchase #5	$81.61	6.485%	$86.9024	$86.90	$86.90	$86.90
Purchase #6	$206.86	6.584%	$220.4797	$220.48	$220.50	$220.50
Purchase #7	$62.50	4.552%	$65.345	$65.35	$65.35	$65.30
7 purchase totals =	$978.30		$1,028.3732	$1,028.37	$1,028.40	$1,028.30