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	$201.32	5.279%	$211.9477	$211.95	$211.95	$211.90
Purchase #2	$86.78	3.668%	$89.9631	$89.96	$89.95	$90.00
Purchase #3	$229.51	8.181%	$248.2862	$248.29	$248.30	$248.30
Purchase #4	$99.64	3.781%	$103.4074	$103.41	$103.40	$103.40
Purchase #5	$161.86	13.522%	$183.7467	$183.75	$183.75	$183.70
Purchase #6	$239.86	9.456%	$262.5412	$262.54	$262.55	$262.50
Purchase #7	$47.85	5.285%	$50.3789	$50.38	$50.40	$50.40
7 purchase totals =	$1,066.82		$1,150.2712	$1,150.28	$1,150.30	$1,150.20