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	$50.67	10.794%	$56.1393	$56.14	$56.15	$56.10
Purchase #2	$112.99	9.462%	$123.6811	$123.68	$123.70	$123.70
Purchase #3	$159.46	7.334%	$171.1548	$171.15	$171.15	$171.20
Purchase #4	$233.55	7.197%	$250.3586	$250.36	$250.35	$250.40
Purchase #5	$187.78	9.487%	$205.5947	$205.59	$205.60	$205.60
Purchase #6	$79.42	3.314%	$82.052	$82.05	$82.05	$82.10
Purchase #7	$249.36	7.377%	$267.7553	$267.76	$267.75	$267.80
7 purchase totals =	$1,073.23		$1,156.7358	$1,156.73	$1,156.75	$1,156.90