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	$148.90	5.357%	$156.8766	$156.88	$156.90	$156.90
Purchase #2	$31.45	12.560%	$35.4001	$35.40	$35.40	$35.40
Purchase #3	$13.43	4.535%	$14.0391	$14.04	$14.05	$14.00
Purchase #4	$53.42	6.781%	$57.0424	$57.04	$57.05	$57.00
Purchase #5	$95.56	4.360%	$99.7264	$99.73	$99.75	$99.70
Purchase #6	$103.41	11.225%	$115.0178	$115.02	$115.00	$115.00
Purchase #7	$110.64	9.162%	$120.7768	$120.78	$120.80	$120.80
7 purchase totals =	$556.81		$598.8792	$598.89	$598.95	$598.80