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	$125.73	12.248%	$141.1294	$141.13	$141.15	$141.10
Purchase #2	$85.88	6.479%	$91.4442	$91.44	$91.45	$91.40
Purchase #3	$44.64	4.550%	$46.6711	$46.67	$46.65	$46.70
Purchase #4	$170.55	5.149%	$179.3316	$179.33	$179.35	$179.30
Purchase #5	$188.89	4.207%	$196.8366	$196.84	$196.85	$196.80
Purchase #6	$199.65	11.867%	$223.3425	$223.34	$223.35	$223.30
Purchase #7	$90.79	5.211%	$95.5211	$95.52	$95.50	$95.50
7 purchase totals =	$906.13		$974.2765	$974.27	$974.30	$974.10