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	$49.71	8.278%	$53.825	$53.83	$53.85	$53.80
Purchase #2	$230.97	7.512%	$248.3205	$248.32	$248.30	$248.30
Purchase #3	$33.56	6.424%	$35.7159	$35.72	$35.70	$35.70
Purchase #4	$182.66	9.758%	$200.484	$200.48	$200.50	$200.50
Purchase #5	$152.44	7.714%	$164.1992	$164.20	$164.20	$164.20
Purchase #6	$249.71	5.412%	$263.2243	$263.22	$263.20	$263.20
Purchase #7	$165.97	7.785%	$178.8908	$178.89	$178.90	$178.90
7 purchase totals =	$1,065.02		$1,144.6597	$1,144.66	$1,144.65	$1,144.60