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	$37.98	9.833%	$41.7146	$41.71	$41.70	$41.70
Purchase #2	$50.44	6.339%	$53.6374	$53.64	$53.65	$53.60
Purchase #3	$133.33	6.629%	$142.1684	$142.17	$142.15	$142.20
Purchase #4	$72.55	4.300%	$75.6697	$75.67	$75.65	$75.70
Purchase #5	$184.57	6.226%	$196.0613	$196.06	$196.05	$196.10
Purchase #6	$37.32	11.842%	$41.7394	$41.74	$41.75	$41.70
Purchase #7	$126.33	9.543%	$138.3857	$138.39	$138.40	$138.40
7 purchase totals =	$642.52		$689.3765	$689.38	$689.35	$689.40