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	$118.84	7.507%	$127.7613	$127.76	$127.75	$127.80
Purchase #2	$43.45	10.202%	$47.8828	$47.88	$47.90	$47.90
Purchase #3	$67.91	9.528%	$74.3805	$74.38	$74.40	$74.40
Purchase #4	$244.42	3.646%	$253.3316	$253.33	$253.35	$253.30
Purchase #5	$200.50	10.868%	$222.2903	$222.29	$222.30	$222.30
Purchase #6	$65.27	7.187%	$69.961	$69.96	$69.95	$70.00
Purchase #7	$133.91	9.470%	$146.5913	$146.59	$146.60	$146.60
7 purchase totals =	$874.30		$942.1988	$942.19	$942.25	$942.30