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	$103.41	7.794%	$111.4698	$111.47	$111.45	$111.50
Purchase #2	$64.73	7.460%	$69.5589	$69.56	$69.55	$69.60
Purchase #3	$57.34	3.244%	$59.2001	$59.20	$59.20	$59.20
Purchase #4	$175.83	6.609%	$187.4506	$187.45	$187.45	$187.50
Purchase #5	$60.34	3.207%	$62.2751	$62.28	$62.30	$62.30
Purchase #6	$129.96	11.477%	$144.8755	$144.88	$144.90	$144.90
Purchase #7	$51.65	3.629%	$53.5244	$53.52	$53.50	$53.50
7 purchase totals =	$643.26		$688.3544	$688.36	$688.35	$688.50