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	$165.51	12.396%	$186.0266	$186.03	$186.05	$186.00
Purchase #2	$109.56	4.451%	$114.4365	$114.44	$114.45	$114.40
Purchase #3	$29.64	5.664%	$31.3188	$31.32	$31.30	$31.30
Purchase #4	$155.88	8.242%	$168.7276	$168.73	$168.75	$168.70
Purchase #5	$94.72	7.289%	$101.6241	$101.62	$101.60	$101.60
Purchase #6	$176.31	6.231%	$187.2959	$187.30	$187.30	$187.30
Purchase #7	$210.56	6.134%	$223.4758	$223.48	$223.50	$223.50
7 purchase totals =	$942.18		$1,012.9053	$1,012.92	$1,012.95	$1,012.80