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	$81.73	10.406%	$90.2348	$90.23	$90.25	$90.20
Purchase #2	$80.93	6.861%	$86.4826	$86.48	$86.50	$86.50
Purchase #3	$185.95	5.459%	$196.101	$196.10	$196.10	$196.10
Purchase #4	$9.92	9.658%	$10.8781	$10.88	$10.90	$10.90
Purchase #5	$55.73	13.867%	$63.4581	$63.46	$63.45	$63.50
Purchase #6	$185.83	9.297%	$203.1066	$203.11	$203.10	$203.10
Purchase #7	$88.66	3.234%	$91.5273	$91.53	$91.55	$91.50
7 purchase totals =	$688.75		$741.7885	$741.79	$741.85	$741.80