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	$145.54	7.326%	$156.2023	$156.20	$156.20	$156.20
Purchase #2	$90.33	13.598%	$102.6131	$102.61	$102.60	$102.60
Purchase #3	$162.73	4.559%	$170.1489	$170.15	$170.15	$170.10
Purchase #4	$133.66	4.416%	$139.5624	$139.56	$139.55	$139.60
Purchase #5	$92.27	3.365%	$95.3749	$95.37	$95.35	$95.40
Purchase #6	$164.76	12.664%	$185.6252	$185.63	$185.65	$185.60
Purchase #7	$137.28	10.765%	$152.0582	$152.06	$152.05	$152.10
7 purchase totals =	$926.57		$1,001.5850	$1,001.58	$1,001.55	$1,001.60