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	$135.54	5.587%	$143.1126	$143.11	$143.10	$143.10
Purchase #2	$14.32	11.144%	$15.9158	$15.92	$15.90	$15.90
Purchase #3	$89.85	7.230%	$96.3462	$96.35	$96.35	$96.30
Purchase #4	$130.56	4.600%	$136.5658	$136.57	$136.55	$136.60
Purchase #5	$78.41	4.656%	$82.0608	$82.06	$82.05	$82.10
Purchase #6	$17.44	4.574%	$18.2377	$18.24	$18.25	$18.20
Purchase #7	$117.94	4.830%	$123.6365	$123.64	$123.65	$123.60
7 purchase totals =	$584.06		$615.8754	$615.89	$615.85	$615.80