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	$164.44	12.720%	$185.3568	$185.36	$185.35	$185.40
Purchase #2	$167.50	8.376%	$181.5298	$181.53	$181.55	$181.50
Purchase #3	$41.42	6.501%	$44.1127	$44.11	$44.10	$44.10
Purchase #4	$171.30	10.729%	$189.6788	$189.68	$189.70	$189.70
Purchase #5	$160.86	6.566%	$171.4221	$171.42	$171.40	$171.40
Purchase #6	$198.77	4.780%	$208.2712	$208.27	$208.25	$208.30
Purchase #7	$117.76	11.392%	$131.1752	$131.18	$131.20	$131.20
7 purchase totals =	$1,022.05		$1,111.5466	$1,111.55	$1,111.55	$1,111.60