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	$207.65	7.767%	$223.7782	$223.78	$223.80	$223.80
Purchase #2	$170.73	6.202%	$181.3187	$181.32	$181.30	$181.30
Purchase #3	$141.38	7.151%	$151.4901	$151.49	$151.50	$151.50
Purchase #4	$125.95	10.641%	$139.3523	$139.35	$139.35	$139.40
Purchase #5	$146.72	13.832%	$167.0143	$167.01	$167.00	$167.00
Purchase #6	$53.88	9.419%	$58.955	$58.96	$58.95	$59.00
Purchase #7	$147.84	9.765%	$162.2766	$162.28	$162.30	$162.30
7 purchase totals =	$994.15		$1,084.1852	$1,084.19	$1,084.20	$1,084.30