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	$179.47	10.257%	$197.8782	$197.88	$197.90	$197.90
Purchase #2	$138.88	6.771%	$148.2836	$148.28	$148.30	$148.30
Purchase #3	$81.33	4.719%	$85.168	$85.17	$85.15	$85.20
Purchase #4	$82.76	7.607%	$89.0556	$89.06	$89.05	$89.10
Purchase #5	$68.41	7.347%	$73.4361	$73.44	$73.45	$73.40
Purchase #6	$191.55	12.202%	$214.9229	$214.92	$214.90	$214.90
Purchase #7	$158.72	3.788%	$164.7323	$164.73	$164.75	$164.70
7 purchase totals =	$901.12		$973.4767	$973.48	$973.50	$973.50