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	$162.36	13.852%	$184.8501	$184.85	$184.85	$184.90
Purchase #2	$25.45	6.653%	$27.1432	$27.14	$27.15	$27.10
Purchase #3	$172.82	7.227%	$185.3097	$185.31	$185.30	$185.30
Purchase #4	$71.76	3.546%	$74.3046	$74.30	$74.30	$74.30
Purchase #5	$84.30	6.227%	$89.5494	$89.55	$89.55	$89.50
Purchase #6	$203.80	3.703%	$211.3467	$211.35	$211.35	$211.30
Purchase #7	$115.47	6.502%	$122.9779	$122.98	$123.00	$123.00
7 purchase totals =	$835.96		$895.4816	$895.48	$895.50	$895.40