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	$62.93	10.578%	$69.5867	$69.59	$69.60	$69.60
Purchase #2	$168.34	4.279%	$175.5433	$175.54	$175.55	$175.50
Purchase #3	$38.56	4.450%	$40.2759	$40.28	$40.30	$40.30
Purchase #4	$228.43	11.363%	$254.3865	$254.39	$254.40	$254.40
Purchase #5	$100.70	10.433%	$111.206	$111.21	$111.20	$111.20
Purchase #6	$164.33	13.760%	$186.9418	$186.94	$186.95	$186.90
Purchase #7	$40.46	13.229%	$45.8125	$45.81	$45.80	$45.80
7 purchase totals =	$803.75		$883.7527	$883.76	$883.80	$883.70