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	$219.29	4.628%	$229.4387	$229.44	$229.45	$229.40
Purchase #2	$179.52	5.776%	$189.8891	$189.89	$189.90	$189.90
Purchase #3	$179.88	3.630%	$186.4096	$186.41	$186.40	$186.40
Purchase #4	$81.83	6.415%	$87.0794	$87.08	$87.10	$87.10
Purchase #5	$164.71	10.696%	$182.3274	$182.33	$182.35	$182.30
Purchase #6	$32.64	13.781%	$37.1381	$37.14	$37.15	$37.10
Purchase #7	$42.96	13.331%	$48.687	$48.69	$48.70	$48.70
7 purchase totals =	$900.83		$960.9693	$960.98	$961.05	$960.90