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	$77.68	11.364%	$86.5076	$86.51	$86.50	$86.50
Purchase #2	$86.36	3.584%	$89.4551	$89.46	$89.45	$89.50
Purchase #3	$243.95	6.289%	$259.292	$259.29	$259.30	$259.30
Purchase #4	$165.86	11.853%	$185.5194	$185.52	$185.50	$185.50
Purchase #5	$63.33	9.199%	$69.1557	$69.16	$69.15	$69.20
Purchase #6	$139.43	10.152%	$153.5849	$153.58	$153.60	$153.60
Purchase #7	$168.40	3.867%	$174.912	$174.91	$174.90	$174.90
7 purchase totals =	$945.01		$1,018.4267	$1,018.43	$1,018.40	$1,018.50