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	$73.66	9.751%	$80.8426	$80.84	$80.85	$80.80
Purchase #2	$230.44	5.456%	$243.0128	$243.01	$243.00	$243.00
Purchase #3	$121.86	6.698%	$130.0222	$130.02	$130.00	$130.00
Purchase #4	$92.40	12.703%	$104.1376	$104.14	$104.15	$104.10
Purchase #5	$156.56	11.829%	$175.0795	$175.08	$175.10	$175.10
Purchase #6	$172.38	7.551%	$185.3964	$185.40	$185.40	$185.40
Purchase #7	$89.93	5.541%	$94.913	$94.91	$94.90	$94.90
7 purchase totals =	$937.23		$1,013.4041	$1,013.40	$1,013.40	$1,013.30