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	$86.56	4.116%	$90.1228	$90.12	$90.10	$90.10
Purchase #2	$173.86	8.663%	$188.9215	$188.92	$188.90	$188.90
Purchase #3	$164.86	9.746%	$180.9273	$180.93	$180.95	$180.90
Purchase #4	$91.42	7.808%	$98.5581	$98.56	$98.55	$98.60
Purchase #5	$54.62	7.478%	$58.7045	$58.70	$58.70	$58.70
Purchase #6	$193.60	11.818%	$216.4796	$216.48	$216.50	$216.50
Purchase #7	$198.86	10.838%	$220.4124	$220.41	$220.40	$220.40
7 purchase totals =	$963.78		$1,054.1262	$1,054.12	$1,054.10	$1,054.10