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	$94.44	10.549%	$104.4025	$104.40	$104.40	$104.40
Purchase #2	$240.46	11.571%	$268.2836	$268.28	$268.30	$268.30
Purchase #3	$50.83	6.158%	$53.9601	$53.96	$53.95	$54.00
Purchase #4	$42.88	6.115%	$45.5021	$45.50	$45.50	$45.50
Purchase #5	$181.36	7.163%	$194.3508	$194.35	$194.35	$194.40
Purchase #6	$86.77	3.594%	$89.8885	$89.89	$89.90	$89.90
Purchase #7	$139.50	13.739%	$158.6659	$158.67	$158.65	$158.70
7 purchase totals =	$836.24		$915.0535	$915.05	$915.05	$915.20