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	$172.73	3.466%	$178.7168	$178.72	$178.70	$178.70
Purchase #2	$240.98	9.386%	$263.5984	$263.60	$263.60	$263.60
Purchase #3	$188.62	3.355%	$194.9482	$194.95	$194.95	$194.90
Purchase #4	$62.86	7.287%	$67.4406	$67.44	$67.45	$67.40
Purchase #5	$92.36	8.717%	$100.411	$100.41	$100.40	$100.40
Purchase #6	$132.44	11.818%	$148.0918	$148.09	$148.10	$148.10
Purchase #7	$96.29	6.360%	$102.414	$102.41	$102.40	$102.40
7 purchase totals =	$986.28		$1,055.6208	$1,055.62	$1,055.60	$1,055.50