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	$25.39	4.598%	$26.5574	$26.56	$26.55	$26.60
Purchase #2	$47.28	10.385%	$52.19	$52.19	$52.20	$52.20
Purchase #3	$179.61	9.604%	$196.8597	$196.86	$196.85	$196.90
Purchase #4	$72.77	10.167%	$80.1685	$80.17	$80.15	$80.20
Purchase #5	$101.25	12.473%	$113.8789	$113.88	$113.90	$113.90
Purchase #6	$67.44	3.275%	$69.6487	$69.65	$69.65	$69.60
Purchase #7	$165.51	11.841%	$185.108	$185.11	$185.10	$185.10
7 purchase totals =	$659.25		$724.4112	$724.42	$724.40	$724.50