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	$149.95	11.663%	$167.4387	$167.44	$167.45	$167.40
Purchase #2	$105.95	10.558%	$117.1362	$117.14	$117.15	$117.10
Purchase #3	$202.57	11.158%	$225.1728	$225.17	$225.15	$225.20
Purchase #4	$189.40	11.445%	$211.0768	$211.08	$211.10	$211.10
Purchase #5	$246.51	7.548%	$265.1166	$265.12	$265.10	$265.10
Purchase #6	$10.85	13.129%	$12.2745	$12.27	$12.25	$12.30
Purchase #7	$98.98	3.392%	$102.3374	$102.34	$102.35	$102.30
7 purchase totals =	$1,004.21		$1,100.5530	$1,100.56	$1,100.55	$1,100.50