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	$87.61	3.332%	$90.5292	$90.53	$90.55	$90.50
Purchase #2	$184.48	5.457%	$194.5471	$194.55	$194.55	$194.50
Purchase #3	$241.35	11.346%	$268.7336	$268.73	$268.75	$268.70
Purchase #4	$47.48	13.609%	$53.9416	$53.94	$53.95	$53.90
Purchase #5	$164.41	7.162%	$176.185	$176.19	$176.20	$176.20
Purchase #6	$45.72	3.366%	$47.2589	$47.26	$47.25	$47.30
Purchase #7	$180.50	4.211%	$188.1009	$188.10	$188.10	$188.10
7 purchase totals =	$951.55		$1,019.2963	$1,019.30	$1,019.35	$1,019.20