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	$186.28	4.648%	$194.9383	$194.94	$194.95	$194.90
Purchase #2	$72.82	13.481%	$82.6369	$82.64	$82.65	$82.60
Purchase #3	$181.96	6.793%	$194.3205	$194.32	$194.30	$194.30
Purchase #4	$127.50	4.617%	$133.3867	$133.39	$133.40	$133.40
Purchase #5	$154.80	8.233%	$167.5447	$167.54	$167.55	$167.50
Purchase #6	$94.85	7.693%	$102.1468	$102.15	$102.15	$102.10
Purchase #7	$250.69	10.666%	$277.4286	$277.43	$277.45	$277.40
7 purchase totals =	$1,068.90		$1,152.4025	$1,152.41	$1,152.45	$1,152.20