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	$205.94	12.673%	$232.0388	$232.04	$232.05	$232.00
Purchase #2	$118.87	3.514%	$123.0471	$123.05	$123.05	$123.00
Purchase #3	$110.30	9.183%	$120.4288	$120.43	$120.45	$120.40
Purchase #4	$225.39	6.812%	$240.7436	$240.74	$240.75	$240.70
Purchase #5	$157.46	10.270%	$173.6311	$173.63	$173.65	$173.60
Purchase #6	$186.35	5.668%	$196.9123	$196.91	$196.90	$196.90
Purchase #7	$81.92	4.658%	$85.7358	$85.74	$85.75	$85.70
7 purchase totals =	$1,086.23		$1,172.5375	$1,172.54	$1,172.60	$1,172.30