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	$140.76	9.760%	$154.4982	$154.50	$154.50	$154.50
Purchase #2	$171.67	9.538%	$188.0439	$188.04	$188.05	$188.00
Purchase #3	$200.38	13.862%	$228.1567	$228.16	$228.15	$228.20
Purchase #4	$22.88	6.214%	$24.3018	$24.30	$24.30	$24.30
Purchase #5	$249.95	11.444%	$278.5543	$278.55	$278.55	$278.60
Purchase #6	$64.49	5.287%	$67.8996	$67.90	$67.90	$67.90
Purchase #7	$176.60	5.590%	$186.4719	$186.47	$186.45	$186.50
7 purchase totals =	$1,026.73		$1,127.9264	$1,127.92	$1,127.90	$1,128.00