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	$204.34	7.579%	$219.8269	$219.83	$219.85	$219.80
Purchase #2	$178.27	6.491%	$189.8415	$189.84	$189.85	$189.80
Purchase #3	$64.86	7.666%	$69.8322	$69.83	$69.85	$69.80
Purchase #4	$240.83	5.625%	$254.3767	$254.38	$254.40	$254.40
Purchase #5	$175.46	3.231%	$181.1291	$181.13	$181.15	$181.10
Purchase #6	$150.80	11.517%	$168.1676	$168.17	$168.15	$168.20
Purchase #7	$131.33	7.169%	$140.745	$140.75	$140.75	$140.70
7 purchase totals =	$1,145.89		$1,223.9190	$1,223.93	$1,224.00	$1,223.80