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	$98.79	5.449%	$104.1731	$104.17	$104.15	$104.20
Purchase #2	$156.31	9.608%	$171.3283	$171.33	$171.35	$171.30
Purchase #3	$86.43	6.780%	$92.29	$92.29	$92.30	$92.30
Purchase #4	$10.82	6.448%	$11.5177	$11.52	$11.50	$11.50
Purchase #5	$197.78	4.558%	$206.7948	$206.79	$206.80	$206.80
Purchase #6	$83.65	7.222%	$89.6912	$89.69	$89.70	$89.70
Purchase #7	$250.47	3.115%	$258.2721	$258.27	$258.25	$258.30
7 purchase totals =	$884.25		$934.0672	$934.06	$934.05	$934.10