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	$197.28	6.597%	$210.2946	$210.29	$210.30	$210.30
Purchase #2	$177.89	12.498%	$200.1227	$200.12	$200.10	$200.10
Purchase #3	$91.98	6.856%	$98.2861	$98.29	$98.30	$98.30
Purchase #4	$85.43	6.302%	$90.8138	$90.81	$90.80	$90.80
Purchase #5	$75.95	12.319%	$85.3063	$85.31	$85.30	$85.30
Purchase #6	$47.85	6.747%	$51.0784	$51.08	$51.10	$51.10
Purchase #7	$158.68	9.640%	$173.9768	$173.98	$174.00	$174.00
7 purchase totals =	$835.06		$909.8787	$909.88	$909.90	$909.90