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	$245.95	3.601%	$254.8067	$254.81	$254.80	$254.80
Purchase #2	$191.78	3.294%	$198.0972	$198.10	$198.10	$198.10
Purchase #3	$200.54	6.415%	$213.4046	$213.40	$213.40	$213.40
Purchase #4	$42.84	8.404%	$46.4403	$46.44	$46.45	$46.40
Purchase #5	$86.67	10.588%	$95.8466	$95.85	$95.85	$95.80
Purchase #6	$182.94	7.251%	$196.205	$196.21	$196.20	$196.20
Purchase #7	$90.56	8.623%	$98.369	$98.37	$98.35	$98.40
7 purchase totals =	$1,041.28		$1,103.1694	$1,103.18	$1,103.15	$1,103.10