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	$135.92	12.509%	$152.9222	$152.92	$152.90	$152.90
Purchase #2	$181.74	3.641%	$188.3572	$188.36	$188.35	$188.40
Purchase #3	$35.88	3.410%	$37.1035	$37.10	$37.10	$37.10
Purchase #4	$205.57	8.626%	$223.3025	$223.30	$223.30	$223.30
Purchase #5	$120.54	11.729%	$134.6781	$134.68	$134.70	$134.70
Purchase #6	$43.50	4.332%	$45.3844	$45.38	$45.40	$45.40
Purchase #7	$149.25	12.851%	$168.4301	$168.43	$168.45	$168.40
7 purchase totals =	$872.40		$950.1780	$950.17	$950.20	$950.20