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	$44.97	3.313%	$46.4599	$46.46	$46.45	$46.50
Purchase #2	$67.75	5.119%	$71.2181	$71.22	$71.20	$71.20
Purchase #3	$129.60	11.355%	$144.3161	$144.32	$144.30	$144.30
Purchase #4	$96.73	7.838%	$104.3117	$104.31	$104.30	$104.30
Purchase #5	$141.94	10.217%	$156.442	$156.44	$156.45	$156.40
Purchase #6	$156.86	9.343%	$171.5154	$171.52	$171.50	$171.50
Purchase #7	$90.90	11.407%	$101.269	$101.27	$101.25	$101.30
7 purchase totals =	$728.75		$795.5322	$795.54	$795.45	$795.50