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	$21.57	5.591%	$22.776	$22.78	$22.80	$22.80
Purchase #2	$59.52	10.271%	$65.6333	$65.63	$65.65	$65.60
Purchase #3	$67.50	10.441%	$74.5477	$74.55	$74.55	$74.50
Purchase #4	$139.46	9.450%	$152.639	$152.64	$152.65	$152.60
Purchase #5	$41.43	5.445%	$43.6859	$43.69	$43.70	$43.70
Purchase #6	$17.84	3.751%	$18.5092	$18.51	$18.50	$18.50
Purchase #7	$100.46	9.564%	$110.068	$110.07	$110.05	$110.10
7 purchase totals =	$447.78		$487.8591	$487.87	$487.90	$487.80