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	$100.72	4.841%	$105.5959	$105.60	$105.60	$105.60
Purchase #2	$131.69	4.296%	$137.3474	$137.35	$137.35	$137.30
Purchase #3	$42.51	12.277%	$47.729	$47.73	$47.75	$47.70
Purchase #4	$150.99	8.836%	$164.3315	$164.33	$164.35	$164.30
Purchase #5	$61.37	9.376%	$67.1241	$67.12	$67.10	$67.10
Purchase #6	$248.96	10.512%	$275.1307	$275.13	$275.15	$275.10
Purchase #7	$10.73	5.397%	$11.3091	$11.31	$11.30	$11.30
7 purchase totals =	$746.97		$808.5677	$808.57	$808.60	$808.40