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	$86.27	6.152%	$91.5773	$91.58	$91.60	$91.60
Purchase #2	$62.98	13.594%	$71.5415	$71.54	$71.55	$71.50
Purchase #3	$158.73	13.174%	$179.6411	$179.64	$179.65	$179.60
Purchase #4	$211.77	11.445%	$236.0071	$236.01	$236.00	$236.00
Purchase #5	$238.38	12.586%	$268.3825	$268.38	$268.40	$268.40
Purchase #6	$5.69	10.573%	$6.2916	$6.29	$6.30	$6.30
Purchase #7	$218.68	13.629%	$248.4839	$248.48	$248.50	$248.50
7 purchase totals =	$982.50		$1,101.9250	$1,101.92	$1,102.00	$1,101.90