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	$85.46	12.534%	$96.1716	$96.17	$96.15	$96.20
Purchase #2	$80.97	12.465%	$91.0629	$91.06	$91.05	$91.10
Purchase #3	$186.45	7.477%	$200.3909	$200.39	$200.40	$200.40
Purchase #4	$75.76	7.502%	$81.4435	$81.44	$81.45	$81.40
Purchase #5	$210.32	4.671%	$220.144	$220.14	$220.15	$220.10
Purchase #6	$82.80	11.313%	$92.1672	$92.17	$92.15	$92.20
Purchase #7	$245.52	8.123%	$265.4636	$265.46	$265.45	$265.50
7 purchase totals =	$967.28		$1,046.8437	$1,046.83	$1,046.80	$1,046.90