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	$168.52	7.369%	$180.9382	$180.94	$180.95	$180.90
Purchase #2	$113.79	11.665%	$127.0636	$127.06	$127.05	$127.10
Purchase #3	$39.93	13.347%	$45.2595	$45.26	$45.25	$45.30
Purchase #4	$123.70	6.370%	$131.5797	$131.58	$131.60	$131.60
Purchase #5	$104.35	10.127%	$114.9175	$114.92	$114.90	$114.90
Purchase #6	$38.76	4.541%	$40.5201	$40.52	$40.50	$40.50
Purchase #7	$204.94	4.729%	$214.6316	$214.63	$214.65	$214.60
7 purchase totals =	$793.99		$854.9102	$854.91	$854.90	$854.90