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	$168.89	4.592%	$176.6454	$176.65	$176.65	$176.60
Purchase #2	$35.91	12.148%	$40.2723	$40.27	$40.25	$40.30
Purchase #3	$180.75	4.562%	$188.9958	$189.00	$189.00	$189.00
Purchase #4	$175.94	8.558%	$190.9969	$191.00	$191.00	$191.00
Purchase #5	$111.88	10.452%	$123.5737	$123.57	$123.55	$123.60
Purchase #6	$157.79	6.435%	$167.9438	$167.94	$167.95	$167.90
Purchase #7	$186.27	7.650%	$200.5197	$200.52	$200.50	$200.50
7 purchase totals =	$1,017.43		$1,088.9476	$1,088.95	$1,088.90	$1,088.90