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	$161.33	8.441%	$174.9479	$174.95	$174.95	$174.90
Purchase #2	$225.78	12.187%	$253.2958	$253.30	$253.30	$253.30
Purchase #3	$172.49	13.779%	$196.2574	$196.26	$196.25	$196.30
Purchase #4	$72.65	13.175%	$82.2216	$82.22	$82.20	$82.20
Purchase #5	$127.92	7.716%	$137.7903	$137.79	$137.80	$137.80
Purchase #6	$160.90	10.835%	$178.3335	$178.33	$178.35	$178.30
Purchase #7	$137.47	7.524%	$147.8132	$147.81	$147.80	$147.80
7 purchase totals =	$1,058.54		$1,170.6597	$1,170.66	$1,170.65	$1,170.60