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	$224.97	10.696%	$249.0328	$249.03	$249.05	$249.00
Purchase #2	$72.26	5.549%	$76.2697	$76.27	$76.25	$76.30
Purchase #3	$201.57	13.619%	$229.0218	$229.02	$229.00	$229.00
Purchase #4	$86.83	3.390%	$89.7735	$89.77	$89.75	$89.80
Purchase #5	$194.90	10.461%	$215.2885	$215.29	$215.30	$215.30
Purchase #6	$86.48	3.834%	$89.7956	$89.80	$89.80	$89.80
Purchase #7	$197.96	13.819%	$225.3161	$225.32	$225.30	$225.30
7 purchase totals =	$1,064.97		$1,174.4980	$1,174.50	$1,174.45	$1,174.50