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	$47.71	7.485%	$51.2811	$51.28	$51.30	$51.30
Purchase #2	$174.32	7.567%	$187.5108	$187.51	$187.50	$187.50
Purchase #3	$53.83	9.618%	$59.0074	$59.01	$59.00	$59.00
Purchase #4	$139.64	12.346%	$156.88	$156.88	$156.90	$156.90
Purchase #5	$96.61	4.647%	$101.0995	$101.10	$101.10	$101.10
Purchase #6	$151.67	8.690%	$164.8501	$164.85	$164.85	$164.90
Purchase #7	$193.67	4.276%	$201.9513	$201.95	$201.95	$202.00
7 purchase totals =	$857.45		$922.5802	$922.58	$922.60	$922.70