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	$110.52	3.427%	$114.3075	$114.31	$114.30	$114.30
Purchase #2	$227.27	12.588%	$255.8787	$255.88	$255.90	$255.90
Purchase #3	$202.71	4.221%	$211.2664	$211.27	$211.25	$211.30
Purchase #4	$56.37	5.243%	$59.3255	$59.33	$59.35	$59.30
Purchase #5	$236.34	9.432%	$258.6316	$258.63	$258.65	$258.60
Purchase #6	$35.95	5.260%	$37.841	$37.84	$37.85	$37.80
Purchase #7	$114.77	11.325%	$127.7677	$127.77	$127.75	$127.80
7 purchase totals =	$983.93		$1,065.0184	$1,065.03	$1,065.05	$1,065.00