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	$76.41	7.514%	$82.1514	$82.15	$82.15	$82.20
Purchase #2	$203.83	7.606%	$219.3333	$219.33	$219.35	$219.30
Purchase #3	$50.93	9.413%	$55.724	$55.72	$55.70	$55.70
Purchase #4	$163.49	11.266%	$181.9088	$181.91	$181.90	$181.90
Purchase #5	$63.27	11.487%	$70.5378	$70.54	$70.55	$70.50
Purchase #6	$243.82	12.226%	$273.6294	$273.63	$273.65	$273.60
Purchase #7	$156.90	4.815%	$164.4547	$164.45	$164.45	$164.50
7 purchase totals =	$958.65		$1,047.7394	$1,047.73	$1,047.75	$1,047.70