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	$102.64	4.593%	$107.3543	$107.35	$107.35	$107.40
Purchase #2	$212.29	4.686%	$222.2379	$222.24	$222.25	$222.20
Purchase #3	$54.97	12.685%	$61.9429	$61.94	$61.95	$61.90
Purchase #4	$131.30	12.233%	$147.3619	$147.36	$147.35	$147.40
Purchase #5	$83.68	8.457%	$90.7568	$90.76	$90.75	$90.80
Purchase #6	$180.56	8.627%	$196.1369	$196.14	$196.15	$196.10
Purchase #7	$173.67	5.768%	$183.6873	$183.69	$183.70	$183.70
7 purchase totals =	$939.11		$1,009.4780	$1,009.48	$1,009.50	$1,009.50