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	$250.58	7.701%	$269.8772	$269.88	$269.90	$269.90
Purchase #2	$153.27	8.355%	$166.0757	$166.08	$166.10	$166.10
Purchase #3	$157.58	13.819%	$179.356	$179.36	$179.35	$179.40
Purchase #4	$178.86	9.713%	$196.2327	$196.23	$196.25	$196.20
Purchase #5	$89.34	7.538%	$96.0744	$96.07	$96.05	$96.10
Purchase #6	$29.32	12.557%	$33.0017	$33.00	$33.00	$33.00
Purchase #7	$132.66	7.281%	$142.319	$142.32	$142.30	$142.30
7 purchase totals =	$991.61		$1,082.9367	$1,082.94	$1,082.95	$1,083.00