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	$221.28	8.590%	$240.288	$240.29	$240.30	$240.30
Purchase #2	$96.84	13.109%	$109.5348	$109.53	$109.55	$109.50
Purchase #3	$201.62	3.306%	$208.2856	$208.29	$208.30	$208.30
Purchase #4	$81.33	5.449%	$85.7617	$85.76	$85.75	$85.80
Purchase #5	$56.89	10.322%	$62.7622	$62.76	$62.75	$62.80
Purchase #6	$114.59	4.202%	$119.4051	$119.41	$119.40	$119.40
Purchase #7	$224.45	4.398%	$234.3213	$234.32	$234.30	$234.30
7 purchase totals =	$997.00		$1,060.3587	$1,060.36	$1,060.35	$1,060.40