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	$78.79	6.800%	$84.1477	$84.15	$84.15	$84.10
Purchase #2	$83.37	7.332%	$89.4827	$89.48	$89.50	$89.50
Purchase #3	$236.71	3.864%	$245.8565	$245.86	$245.85	$245.90
Purchase #4	$216.88	6.665%	$231.3351	$231.34	$231.35	$231.30
Purchase #5	$152.31	6.627%	$162.4036	$162.40	$162.40	$162.40
Purchase #6	$229.76	3.675%	$238.2037	$238.20	$238.20	$238.20
Purchase #7	$108.65	6.599%	$115.8198	$115.82	$115.80	$115.80
7 purchase totals =	$1,106.47		$1,167.2491	$1,167.25	$1,167.25	$1,167.20