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	$75.71	8.442%	$82.1014	$82.10	$82.10	$82.10
Purchase #2	$62.56	7.279%	$67.1137	$67.11	$67.10	$67.10
Purchase #3	$110.78	6.676%	$118.1757	$118.18	$118.20	$118.20
Purchase #4	$57.41	13.342%	$65.0696	$65.07	$65.05	$65.10
Purchase #5	$5.96	13.263%	$6.7505	$6.75	$6.75	$6.80
Purchase #6	$208.86	3.441%	$216.0469	$216.05	$216.05	$216.00
Purchase #7	$178.74	4.394%	$186.5938	$186.59	$186.60	$186.60
7 purchase totals =	$700.02		$741.8516	$741.85	$741.85	$741.90