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	$34.80	8.353%	$37.7068	$37.71	$37.70	$37.70
Purchase #2	$78.48	8.601%	$85.2301	$85.23	$85.25	$85.20
Purchase #3	$226.32	7.511%	$243.3189	$243.32	$243.30	$243.30
Purchase #4	$245.71	8.822%	$267.3865	$267.39	$267.40	$267.40
Purchase #5	$174.92	3.124%	$180.3845	$180.38	$180.40	$180.40
Purchase #6	$216.88	9.718%	$237.9564	$237.96	$237.95	$238.00
Purchase #7	$97.29	3.200%	$100.4033	$100.40	$100.40	$100.40
7 purchase totals =	$1,074.40		$1,152.3865	$1,152.39	$1,152.40	$1,152.40