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	$222.61	3.470%	$230.3346	$230.33	$230.35	$230.30
Purchase #2	$212.86	6.826%	$227.3898	$227.39	$227.40	$227.40
Purchase #3	$64.28	10.837%	$71.246	$71.25	$71.25	$71.20
Purchase #4	$228.33	6.740%	$243.7194	$243.72	$243.70	$243.70
Purchase #5	$75.90	6.856%	$81.1037	$81.10	$81.10	$81.10
Purchase #6	$205.96	11.829%	$230.323	$230.32	$230.30	$230.30
Purchase #7	$41.78	11.341%	$46.5183	$46.52	$46.50	$46.50
7 purchase totals =	$1,051.72		$1,130.6348	$1,130.63	$1,130.60	$1,130.50