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	$233.88	10.544%	$258.5403	$258.54	$258.55	$258.50
Purchase #2	$233.38	13.363%	$264.5666	$264.57	$264.55	$264.60
Purchase #3	$63.31	7.362%	$67.9709	$67.97	$67.95	$68.00
Purchase #4	$29.39	6.446%	$31.2845	$31.28	$31.30	$31.30
Purchase #5	$31.61	4.123%	$32.9133	$32.91	$32.90	$32.90
Purchase #6	$39.87	4.236%	$41.5589	$41.56	$41.55	$41.60
Purchase #7	$5.54	10.207%	$6.1055	$6.11	$6.10	$6.10
7 purchase totals =	$636.98		$702.9400	$702.94	$702.90	$703.00