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	$215.54	6.205%	$228.9143	$228.91	$228.90	$228.90
Purchase #2	$40.57	4.867%	$42.5445	$42.54	$42.55	$42.50
Purchase #3	$112.84	9.293%	$123.3262	$123.33	$123.35	$123.30
Purchase #4	$58.25	9.458%	$63.7593	$63.76	$63.75	$63.80
Purchase #5	$207.73	10.377%	$229.2861	$229.29	$229.30	$229.30
Purchase #6	$231.88	3.800%	$240.6914	$240.69	$240.70	$240.70
Purchase #7	$191.70	3.744%	$198.8772	$198.88	$198.90	$198.90
7 purchase totals =	$1,058.51		$1,127.3990	$1,127.40	$1,127.45	$1,127.40