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	$168.59	10.479%	$186.2565	$186.26	$186.25	$186.30
Purchase #2	$86.89	3.693%	$90.0988	$90.10	$90.10	$90.10
Purchase #3	$162.25	13.123%	$183.5421	$183.54	$183.55	$183.50
Purchase #4	$61.70	8.663%	$67.0451	$67.05	$67.05	$67.00
Purchase #5	$26.67	6.466%	$28.3945	$28.39	$28.40	$28.40
Purchase #6	$66.86	8.126%	$72.293	$72.29	$72.30	$72.30
Purchase #7	$186.91	11.124%	$207.7019	$207.70	$207.70	$207.70
7 purchase totals =	$759.87		$835.3319	$835.33	$835.35	$835.30