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	$56.80	9.257%	$62.058	$62.06	$62.05	$62.10
Purchase #2	$10.68	13.729%	$12.1463	$12.15	$12.15	$12.10
Purchase #3	$177.96	11.722%	$198.8205	$198.82	$198.80	$198.80
Purchase #4	$110.98	11.248%	$123.463	$123.46	$123.45	$123.50
Purchase #5	$162.44	10.227%	$179.0527	$179.05	$179.05	$179.10
Purchase #6	$48.41	8.572%	$52.5597	$52.56	$52.55	$52.60
Purchase #7	$71.76	9.167%	$78.3382	$78.34	$78.35	$78.30
7 purchase totals =	$639.03		$706.4384	$706.44	$706.40	$706.50