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	$221.27	3.280%	$228.5277	$228.53	$228.55	$228.50
Purchase #2	$237.39	5.839%	$251.2512	$251.25	$251.25	$251.30
Purchase #3	$58.90	9.162%	$64.2964	$64.30	$64.30	$64.30
Purchase #4	$238.51	6.715%	$254.5259	$254.53	$254.55	$254.50
Purchase #5	$197.58	12.533%	$222.3427	$222.34	$222.35	$222.30
Purchase #6	$153.27	7.320%	$164.4894	$164.49	$164.50	$164.50
Purchase #7	$173.41	9.714%	$190.255	$190.26	$190.25	$190.30
7 purchase totals =	$1,280.33		$1,375.6883	$1,375.70	$1,375.75	$1,375.70