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	$169.66	3.443%	$175.5014	$175.50	$175.50	$175.50
Purchase #2	$44.65	11.539%	$49.8022	$49.80	$49.80	$49.80
Purchase #3	$22.92	6.659%	$24.4462	$24.45	$24.45	$24.40
Purchase #4	$42.46	7.607%	$45.6899	$45.69	$45.70	$45.70
Purchase #5	$189.69	3.627%	$196.5701	$196.57	$196.55	$196.60
Purchase #6	$147.82	9.267%	$161.5185	$161.52	$161.50	$161.50
Purchase #7	$159.66	11.817%	$178.527	$178.53	$178.55	$178.50
7 purchase totals =	$776.86		$832.0553	$832.06	$832.05	$832.00