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	$237.93	13.331%	$269.6484	$269.65	$269.65	$269.60
Purchase #2	$181.85	4.267%	$189.6095	$189.61	$189.60	$189.60
Purchase #3	$63.36	12.566%	$71.3218	$71.32	$71.30	$71.30
Purchase #4	$66.70	9.147%	$72.801	$72.80	$72.80	$72.80
Purchase #5	$149.55	5.435%	$157.678	$157.68	$157.70	$157.70
Purchase #6	$159.85	4.654%	$167.2894	$167.29	$167.30	$167.30
Purchase #7	$224.54	6.404%	$238.9195	$238.92	$238.90	$238.90
7 purchase totals =	$1,083.78		$1,167.2676	$1,167.27	$1,167.25	$1,167.20