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	$159.91	8.874%	$174.1004	$174.10	$174.10	$174.10
Purchase #2	$79.43	3.633%	$82.3157	$82.32	$82.30	$82.30
Purchase #3	$123.73	4.173%	$128.8933	$128.89	$128.90	$128.90
Purchase #4	$204.41	6.437%	$217.5679	$217.57	$217.55	$217.60
Purchase #5	$168.90	6.444%	$179.7839	$179.78	$179.80	$179.80
Purchase #6	$126.28	3.802%	$131.0812	$131.08	$131.10	$131.10
Purchase #7	$51.94	5.429%	$54.7598	$54.76	$54.75	$54.80
7 purchase totals =	$914.60		$968.5022	$968.50	$968.50	$968.60