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	$236.84	11.581%	$264.2684	$264.27	$264.25	$264.30
Purchase #2	$174.26	5.131%	$183.2013	$183.20	$183.20	$183.20
Purchase #3	$217.61	5.235%	$229.0019	$229.00	$229.00	$229.00
Purchase #4	$112.71	8.600%	$122.4031	$122.40	$122.40	$122.40
Purchase #5	$67.30	7.422%	$72.295	$72.30	$72.30	$72.30
Purchase #6	$37.53	11.332%	$41.7829	$41.78	$41.80	$41.80
Purchase #7	$84.76	5.379%	$89.3192	$89.32	$89.30	$89.30
7 purchase totals =	$931.01		$1,002.2718	$1,002.27	$1,002.25	$1,002.30