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	$202.72	6.814%	$216.5333	$216.53	$216.55	$216.50
Purchase #2	$114.98	4.623%	$120.2955	$120.30	$120.30	$120.30
Purchase #3	$97.33	6.106%	$103.273	$103.27	$103.25	$103.30
Purchase #4	$202.91	8.387%	$219.9281	$219.93	$219.95	$219.90
Purchase #5	$96.27	11.705%	$107.5384	$107.54	$107.55	$107.50
Purchase #6	$138.77	6.492%	$147.7789	$147.78	$147.80	$147.80
Purchase #7	$179.30	9.322%	$196.0143	$196.01	$196.00	$196.00
7 purchase totals =	$1,032.28		$1,111.3615	$1,111.36	$1,111.40	$1,111.30