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	$144.81	5.360%	$152.5718	$152.57	$152.55	$152.60
Purchase #2	$164.88	13.440%	$187.0399	$187.04	$187.05	$187.00
Purchase #3	$147.88	12.463%	$166.3103	$166.31	$166.30	$166.30
Purchase #4	$164.86	12.132%	$184.8608	$184.86	$184.85	$184.90
Purchase #5	$232.99	9.112%	$254.22	$254.22	$254.20	$254.20
Purchase #6	$132.67	4.152%	$138.1785	$138.18	$138.20	$138.20
Purchase #7	$112.46	13.437%	$127.5713	$127.57	$127.55	$127.60
7 purchase totals =	$1,100.55		$1,210.7526	$1,210.75	$1,210.70	$1,210.80