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	$79.82	11.216%	$88.7726	$88.77	$88.75	$88.80
Purchase #2	$152.38	3.818%	$158.1979	$158.20	$158.20	$158.20
Purchase #3	$99.83	13.815%	$113.6215	$113.62	$113.60	$113.60
Purchase #4	$66.76	4.223%	$69.5793	$69.58	$69.60	$69.60
Purchase #5	$213.84	4.423%	$223.2981	$223.30	$223.30	$223.30
Purchase #6	$139.71	13.749%	$158.9187	$158.92	$158.90	$158.90
Purchase #7	$221.41	9.514%	$242.4749	$242.47	$242.45	$242.50
7 purchase totals =	$973.75		$1,054.8630	$1,054.86	$1,054.80	$1,054.90