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	$170.95	4.819%	$179.1881	$179.19	$179.20	$179.20
Purchase #2	$184.75	7.769%	$199.1032	$199.10	$199.10	$199.10
Purchase #3	$123.51	12.113%	$138.4708	$138.47	$138.45	$138.50
Purchase #4	$212.98	9.653%	$233.539	$233.54	$233.55	$233.50
Purchase #5	$211.81	8.269%	$229.3246	$229.32	$229.30	$229.30
Purchase #6	$127.84	11.719%	$142.8216	$142.82	$142.80	$142.80
Purchase #7	$79.65	11.771%	$89.0256	$89.03	$89.05	$89.00
7 purchase totals =	$1,111.49		$1,211.4729	$1,211.47	$1,211.45	$1,211.40