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	$198.75	7.264%	$213.1872	$213.19	$213.20	$213.20
Purchase #2	$54.29	10.353%	$59.9106	$59.91	$59.90	$59.90
Purchase #3	$58.39	6.467%	$62.1661	$62.17	$62.15	$62.20
Purchase #4	$139.74	7.565%	$150.3113	$150.31	$150.30	$150.30
Purchase #5	$210.35	6.354%	$223.7156	$223.72	$223.70	$223.70
Purchase #6	$19.69	12.465%	$22.1444	$22.14	$22.15	$22.10
Purchase #7	$172.47	5.711%	$182.3198	$182.32	$182.30	$182.30
7 purchase totals =	$853.68		$913.7550	$913.76	$913.70	$913.70