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	$171.52	7.290%	$184.0238	$184.02	$184.00	$184.00
Purchase #2	$122.79	7.229%	$131.6665	$131.67	$131.65	$131.70
Purchase #3	$161.84	11.607%	$180.6248	$180.62	$180.60	$180.60
Purchase #4	$96.78	12.156%	$108.5446	$108.54	$108.55	$108.50
Purchase #5	$122.52	6.773%	$130.8183	$130.82	$130.80	$130.80
Purchase #6	$142.43	7.286%	$152.8074	$152.81	$152.80	$152.80
Purchase #7	$166.37	4.826%	$174.399	$174.40	$174.40	$174.40
7 purchase totals =	$984.25		$1,062.8844	$1,062.88	$1,062.80	$1,062.80