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	$181.79	6.457%	$193.5282	$193.53	$193.55	$193.50
Purchase #2	$224.43	10.772%	$248.6056	$248.61	$248.60	$248.60
Purchase #3	$68.89	4.229%	$71.8034	$71.80	$71.80	$71.80
Purchase #4	$245.64	10.504%	$271.442	$271.44	$271.45	$271.40
Purchase #5	$82.60	3.774%	$85.7173	$85.72	$85.70	$85.70
Purchase #6	$114.73	7.498%	$123.3325	$123.33	$123.35	$123.30
Purchase #7	$96.84	13.249%	$109.6703	$109.67	$109.65	$109.70
7 purchase totals =	$1,014.92		$1,104.0993	$1,104.10	$1,104.10	$1,104.00