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	$78.70	13.420%	$89.2615	$89.26	$89.25	$89.30
Purchase #2	$103.90	9.239%	$113.4993	$113.50	$113.50	$113.50
Purchase #3	$182.33	10.471%	$201.4218	$201.42	$201.40	$201.40
Purchase #4	$174.31	11.234%	$193.892	$193.89	$193.90	$193.90
Purchase #5	$111.27	11.726%	$124.3175	$124.32	$124.30	$124.30
Purchase #6	$34.71	10.414%	$38.3247	$38.32	$38.30	$38.30
Purchase #7	$218.97	10.173%	$241.2458	$241.25	$241.25	$241.20
7 purchase totals =	$904.19		$1,001.9626	$1,001.96	$1,001.90	$1,001.90