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	$173.55	11.819%	$194.0619	$194.06	$194.05	$194.10
Purchase #2	$137.72	9.180%	$150.3627	$150.36	$150.35	$150.40
Purchase #3	$79.42	11.158%	$88.2817	$88.28	$88.30	$88.30
Purchase #4	$116.55	12.525%	$131.1479	$131.15	$131.15	$131.10
Purchase #5	$183.84	7.874%	$198.3156	$198.32	$198.30	$198.30
Purchase #6	$130.50	4.542%	$136.4273	$136.43	$136.45	$136.40
Purchase #7	$69.48	12.256%	$77.9955	$78.00	$78.00	$78.00
7 purchase totals =	$891.06		$976.5926	$976.60	$976.60	$976.60