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	$84.37	3.670%	$87.4664	$87.47	$87.45	$87.50
Purchase #2	$141.52	6.208%	$150.3056	$150.31	$150.30	$150.30
Purchase #3	$84.75	13.594%	$96.2709	$96.27	$96.25	$96.30
Purchase #4	$184.88	6.135%	$196.2224	$196.22	$196.20	$196.20
Purchase #5	$43.28	4.818%	$45.3652	$45.37	$45.35	$45.40
Purchase #6	$170.66	10.236%	$188.1288	$188.13	$188.15	$188.10
Purchase #7	$155.58	3.311%	$160.7313	$160.73	$160.75	$160.70
7 purchase totals =	$865.04		$924.4906	$924.50	$924.45	$924.50