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	$181.95	7.788%	$196.1203	$196.12	$196.10	$196.10
Purchase #2	$99.40	9.803%	$109.1442	$109.14	$109.15	$109.10
Purchase #3	$27.62	11.472%	$30.7886	$30.79	$30.80	$30.80
Purchase #4	$169.34	7.798%	$182.5451	$182.55	$182.55	$182.50
Purchase #5	$142.92	4.766%	$149.7316	$149.73	$149.75	$149.70
Purchase #6	$237.84	4.499%	$248.5404	$248.54	$248.55	$248.50
Purchase #7	$171.47	6.477%	$182.5761	$182.58	$182.60	$182.60
7 purchase totals =	$1,030.54		$1,099.4463	$1,099.45	$1,099.50	$1,099.30