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	$172.40	13.865%	$196.3033	$196.30	$196.30	$196.30
Purchase #2	$245.36	11.824%	$274.3714	$274.37	$274.35	$274.40
Purchase #3	$45.26	5.277%	$47.6484	$47.65	$47.65	$47.60
Purchase #4	$82.40	8.402%	$89.3232	$89.32	$89.30	$89.30
Purchase #5	$152.85	9.629%	$167.5679	$167.57	$167.55	$167.60
Purchase #6	$182.44	13.736%	$207.5	$207.50	$207.50	$207.50
Purchase #7	$84.32	8.446%	$91.4417	$91.44	$91.45	$91.40
7 purchase totals =	$965.03		$1,074.1559	$1,074.15	$1,074.10	$1,074.10