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	$226.92	11.763%	$253.6126	$253.61	$253.60	$253.60
Purchase #2	$168.54	6.736%	$179.8929	$179.89	$179.90	$179.90
Purchase #3	$86.81	12.818%	$97.9373	$97.94	$97.95	$97.90
Purchase #4	$86.38	5.813%	$91.4013	$91.40	$91.40	$91.40
Purchase #5	$110.91	3.449%	$114.7353	$114.74	$114.75	$114.70
Purchase #6	$166.98	11.104%	$185.5215	$185.52	$185.50	$185.50
Purchase #7	$86.48	4.735%	$90.5748	$90.57	$90.55	$90.60
7 purchase totals =	$933.02		$1,013.6757	$1,013.67	$1,013.65	$1,013.60