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	$223.38	4.857%	$234.2296	$234.23	$234.25	$234.20
Purchase #2	$40.47	12.229%	$45.4191	$45.42	$45.40	$45.40
Purchase #3	$92.91	8.529%	$100.8343	$100.83	$100.85	$100.80
Purchase #4	$115.82	10.633%	$128.1351	$128.14	$128.15	$128.10
Purchase #5	$171.63	10.608%	$189.8365	$189.84	$189.85	$189.80
Purchase #6	$96.80	12.651%	$109.0462	$109.05	$109.05	$109.00
Purchase #7	$217.57	5.587%	$229.7256	$229.73	$229.75	$229.70
7 purchase totals =	$958.58		$1,037.2264	$1,037.24	$1,037.30	$1,037.00