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	$140.77	3.764%	$146.0686	$146.07	$146.05	$146.10
Purchase #2	$98.71	8.432%	$107.0332	$107.03	$107.05	$107.00
Purchase #3	$215.57	6.402%	$229.3708	$229.37	$229.35	$229.40
Purchase #4	$63.93	13.136%	$72.3278	$72.33	$72.35	$72.30
Purchase #5	$191.30	12.290%	$214.8108	$214.81	$214.80	$214.80
Purchase #6	$234.43	6.661%	$250.0454	$250.05	$250.05	$250.00
Purchase #7	$152.89	7.667%	$164.6121	$164.61	$164.60	$164.60
7 purchase totals =	$1,097.60		$1,184.2687	$1,184.27	$1,184.25	$1,184.20