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	$85.51	4.741%	$89.564	$89.56	$89.55	$89.60
Purchase #2	$145.53	4.704%	$152.3757	$152.38	$152.40	$152.40
Purchase #3	$220.78	3.356%	$228.1894	$228.19	$228.20	$228.20
Purchase #4	$249.85	13.182%	$282.7852	$282.79	$282.80	$282.80
Purchase #5	$174.92	3.869%	$181.6877	$181.69	$181.70	$181.70
Purchase #6	$238.95	4.702%	$250.1854	$250.19	$250.20	$250.20
Purchase #7	$65.88	9.290%	$72.0003	$72.00	$72.00	$72.00
7 purchase totals =	$1,181.42		$1,256.7877	$1,256.80	$1,256.85	$1,256.90