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	$170.61	6.576%	$181.8293	$181.83	$181.85	$181.80
Purchase #2	$37.65	6.536%	$40.1108	$40.11	$40.10	$40.10
Purchase #3	$144.78	7.279%	$155.3185	$155.32	$155.30	$155.30
Purchase #4	$205.69	12.661%	$231.7324	$231.73	$231.75	$231.70
Purchase #5	$165.92	13.115%	$187.6804	$187.68	$187.70	$187.70
Purchase #6	$87.53	9.842%	$96.1447	$96.14	$96.15	$96.10
Purchase #7	$151.58	7.124%	$162.3786	$162.38	$162.40	$162.40
7 purchase totals =	$963.76		$1,055.1947	$1,055.19	$1,055.25	$1,055.10