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	$73.61	5.865%	$77.9272	$77.93	$77.95	$77.90
Purchase #2	$142.81	13.803%	$162.5221	$162.52	$162.50	$162.50
Purchase #3	$183.67	5.374%	$193.5404	$193.54	$193.55	$193.50
Purchase #4	$145.96	3.124%	$150.5198	$150.52	$150.50	$150.50
Purchase #5	$180.88	5.545%	$190.9098	$190.91	$190.90	$190.90
Purchase #6	$91.41	11.409%	$101.839	$101.84	$101.85	$101.80
Purchase #7	$238.47	11.282%	$265.3742	$265.37	$265.35	$265.40
7 purchase totals =	$1,056.81		$1,142.6325	$1,142.63	$1,142.60	$1,142.50