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	$54.87	10.713%	$60.7482	$60.75	$60.75	$60.70
Purchase #2	$81.38	6.803%	$86.9163	$86.92	$86.90	$86.90
Purchase #3	$137.48	4.654%	$143.8783	$143.88	$143.90	$143.90
Purchase #4	$154.43	13.362%	$175.0649	$175.06	$175.05	$175.10
Purchase #5	$101.43	6.613%	$108.1376	$108.14	$108.15	$108.10
Purchase #6	$111.83	13.839%	$127.3062	$127.31	$127.30	$127.30
Purchase #7	$247.79	4.165%	$258.1105	$258.11	$258.10	$258.10
7 purchase totals =	$889.21		$960.1620	$960.17	$960.15	$960.10