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	$245.50	3.407%	$253.8642	$253.86	$253.85	$253.90
Purchase #2	$182.60	3.191%	$188.4268	$188.43	$188.45	$188.40
Purchase #3	$187.85	4.468%	$196.2431	$196.24	$196.25	$196.20
Purchase #4	$178.81	11.732%	$199.788	$199.79	$199.80	$199.80
Purchase #5	$154.80	8.197%	$167.489	$167.49	$167.50	$167.50
Purchase #6	$26.73	5.127%	$28.1004	$28.10	$28.10	$28.10
Purchase #7	$166.69	5.303%	$175.5296	$175.53	$175.55	$175.50
7 purchase totals =	$1,142.98		$1,209.4411	$1,209.44	$1,209.50	$1,209.40