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	$172.89	4.786%	$181.1645	$181.16	$181.15	$181.20
Purchase #2	$85.41	3.345%	$88.267	$88.27	$88.25	$88.30
Purchase #3	$241.52	13.549%	$274.2435	$274.24	$274.25	$274.20
Purchase #4	$145.34	5.188%	$152.8802	$152.88	$152.90	$152.90
Purchase #5	$96.76	8.640%	$105.1201	$105.12	$105.10	$105.10
Purchase #6	$240.58	7.549%	$258.7414	$258.74	$258.75	$258.70
Purchase #7	$69.26	6.204%	$73.5569	$73.56	$73.55	$73.60
7 purchase totals =	$1,051.76		$1,133.9736	$1,133.97	$1,133.95	$1,134.00