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	$210.37	12.512%	$236.6915	$236.69	$236.70	$236.70
Purchase #2	$228.82	4.408%	$238.9064	$238.91	$238.90	$238.90
Purchase #3	$168.71	7.457%	$181.2907	$181.29	$181.30	$181.30
Purchase #4	$57.74	7.582%	$62.1178	$62.12	$62.10	$62.10
Purchase #5	$97.39	12.324%	$109.3923	$109.39	$109.40	$109.40
Purchase #6	$85.84	4.373%	$89.5938	$89.59	$89.60	$89.60
Purchase #7	$126.35	13.746%	$143.7181	$143.72	$143.70	$143.70
7 purchase totals =	$975.22		$1,061.7106	$1,061.71	$1,061.70	$1,061.70