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	$213.91	7.471%	$229.8912	$229.89	$229.90	$229.90
Purchase #2	$202.72	6.610%	$216.1198	$216.12	$216.10	$216.10
Purchase #3	$209.64	3.670%	$217.3338	$217.33	$217.35	$217.30
Purchase #4	$105.88	6.664%	$112.9358	$112.94	$112.95	$112.90
Purchase #5	$135.42	3.759%	$140.5104	$140.51	$140.50	$140.50
Purchase #6	$158.92	5.627%	$167.8624	$167.86	$167.85	$167.90
Purchase #7	$127.58	9.453%	$139.6401	$139.64	$139.65	$139.60
7 purchase totals =	$1,154.07		$1,224.2935	$1,224.29	$1,224.30	$1,224.20