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	$45.57	3.247%	$47.0497	$47.05	$47.05	$47.00
Purchase #2	$166.73	7.471%	$179.1864	$179.19	$179.20	$179.20
Purchase #3	$165.40	4.627%	$173.0531	$173.05	$173.05	$173.10
Purchase #4	$105.89	3.154%	$109.2298	$109.23	$109.25	$109.20
Purchase #5	$132.29	9.787%	$145.2372	$145.24	$145.25	$145.20
Purchase #6	$202.45	9.231%	$221.1382	$221.14	$221.15	$221.10
Purchase #7	$153.33	7.230%	$164.4158	$164.42	$164.40	$164.40
7 purchase totals =	$971.66		$1,039.3102	$1,039.32	$1,039.35	$1,039.20