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	$227.58	8.839%	$247.6958	$247.70	$247.70	$247.70
Purchase #2	$40.88	7.324%	$43.8741	$43.87	$43.85	$43.90
Purchase #3	$99.59	10.704%	$110.2501	$110.25	$110.25	$110.30
Purchase #4	$95.74	11.868%	$107.1024	$107.10	$107.10	$107.10
Purchase #5	$147.66	13.111%	$167.0197	$167.02	$167.00	$167.00
Purchase #6	$51.48	3.148%	$53.1006	$53.10	$53.10	$53.10
Purchase #7	$84.55	6.837%	$90.3307	$90.33	$90.35	$90.30
7 purchase totals =	$747.48		$819.3734	$819.37	$819.35	$819.40