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	$202.45	10.338%	$223.3793	$223.38	$223.40	$223.40
Purchase #2	$41.98	5.781%	$44.4069	$44.41	$44.40	$44.40
Purchase #3	$68.79	13.827%	$78.3016	$78.30	$78.30	$78.30
Purchase #4	$174.61	13.653%	$198.4495	$198.45	$198.45	$198.40
Purchase #5	$162.31	6.632%	$173.0744	$173.07	$173.05	$173.10
Purchase #6	$111.95	3.367%	$115.7194	$115.72	$115.70	$115.70
Purchase #7	$152.36	12.426%	$171.2923	$171.29	$171.30	$171.30
7 purchase totals =	$914.45		$1,004.6234	$1,004.62	$1,004.60	$1,004.60