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	$176.37	11.253%	$196.2169	$196.22	$196.20	$196.20
Purchase #2	$58.39	6.502%	$62.1865	$62.19	$62.20	$62.20
Purchase #3	$131.89	5.871%	$139.6333	$139.63	$139.65	$139.60
Purchase #4	$50.37	12.839%	$56.837	$56.84	$56.85	$56.80
Purchase #5	$131.53	9.820%	$144.4462	$144.45	$144.45	$144.40
Purchase #6	$95.55	4.337%	$99.694	$99.69	$99.70	$99.70
Purchase #7	$27.76	12.749%	$31.2991	$31.30	$31.30	$31.30
7 purchase totals =	$671.86		$730.3130	$730.32	$730.35	$730.20