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	$232.28	5.216%	$244.3957	$244.40	$244.40	$244.40
Purchase #2	$36.97	10.367%	$40.8027	$40.80	$40.80	$40.80
Purchase #3	$75.83	6.385%	$80.6717	$80.67	$80.65	$80.70
Purchase #4	$152.27	5.211%	$160.2048	$160.20	$160.20	$160.20
Purchase #5	$186.94	5.850%	$197.876	$197.88	$197.90	$197.90
Purchase #6	$111.76	12.374%	$125.5892	$125.59	$125.60	$125.60
Purchase #7	$209.33	6.199%	$222.3064	$222.31	$222.30	$222.30
7 purchase totals =	$1,005.38		$1,071.8465	$1,071.85	$1,071.85	$1,071.90