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	$131.98	7.691%	$142.1306	$142.13	$142.15	$142.10
Purchase #2	$154.36	10.793%	$171.0201	$171.02	$171.00	$171.00
Purchase #3	$242.63	3.699%	$251.6049	$251.60	$251.60	$251.60
Purchase #4	$65.55	9.115%	$71.5249	$71.52	$71.50	$71.50
Purchase #5	$231.79	6.752%	$247.4405	$247.44	$247.45	$247.40
Purchase #6	$79.64	13.253%	$90.1947	$90.19	$90.20	$90.20
Purchase #7	$100.32	3.323%	$103.6536	$103.65	$103.65	$103.70
7 purchase totals =	$1,006.27		$1,077.5693	$1,077.55	$1,077.55	$1,077.50