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	$100.72	8.612%	$109.394	$109.39	$109.40	$109.40
Purchase #2	$50.87	7.279%	$54.5728	$54.57	$54.55	$54.60
Purchase #3	$68.91	4.650%	$72.1143	$72.11	$72.10	$72.10
Purchase #4	$142.42	3.505%	$147.4118	$147.41	$147.40	$147.40
Purchase #5	$179.36	4.313%	$187.0958	$187.10	$187.10	$187.10
Purchase #6	$76.52	10.865%	$84.8339	$84.83	$84.85	$84.80
Purchase #7	$73.41	6.443%	$78.1398	$78.14	$78.15	$78.10
7 purchase totals =	$692.21		$733.5624	$733.55	$733.55	$733.50