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	$229.27	10.860%	$254.1687	$254.17	$254.15	$254.20
Purchase #2	$99.58	3.392%	$102.9578	$102.96	$102.95	$103.00
Purchase #3	$137.36	4.494%	$143.533	$143.53	$143.55	$143.50
Purchase #4	$25.86	4.512%	$27.0268	$27.03	$27.05	$27.00
Purchase #5	$216.27	13.686%	$245.8687	$245.87	$245.85	$245.90
Purchase #6	$80.54	10.780%	$89.2222	$89.22	$89.20	$89.20
Purchase #7	$165.94	12.125%	$186.0602	$186.06	$186.05	$186.10
7 purchase totals =	$954.82		$1,048.8374	$1,048.84	$1,048.80	$1,048.90